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Unit 11: Chemical Changes Flashcards

1
Q

Chemical Changes - definitions, laws, how reactions are produced etc (6pts)

A
  • A physical change is reversible and does not form new substances. This change is temporary.
  • A chemical change is a change in which a new substance is formed.
  • A chemical change is usually irreversible and forms new substances. This change is permanent.
  • E.g. iron rusting, baked cake
  • When a new substance is made from a chemical change, the process is called a chemical reaction.
  • In a chemical reaction, substances (called reactants) react with each other to form new substances (called products). Usually energy such as thermal, light and/or electricity is taken in or given out during a chemical reaction.
  • The starting substances are the reactants and the new substance formed is called the product.
  • Chemical reactions obey the law of conservation of energy.
  • In a chemical change, energy is neither created nor destroyed, they are either transformed or transferred from one form to another.
  • Chemical reactions obey the law of conservation of mass.
  • In a chemical change, matter is neither created or destroyed in a reaction; they are only rearranged. Mass is conserved. (unchanged)
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2
Q

what is a chemical change?

A
  • A chemical change is a change in which a new substance is formed.
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3
Q

what is a chemical reaction?

A
  • When a new substance is made from a chemical change, the process is called a chemical reaction.
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4
Q

what happens in a chemical reaction? what are the components of a chemical reaction?

A
  • When a new substance is made from a chemical change, the process is called a chemical reaction.
  • In a chemical reaction, substances (called reactants) react with each other to form new substances (called products). Usually energy such as thermal, light and/or electricity is taken in or given out during a chemical reaction.
  • The starting substances are the reactants and the new substance formed is called the product.
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5
Q

what is the law of conservation of energy?

A
  • Chemical reactions obey the law of conservation of energy.
  • In a chemical change, energy is neither created nor destroyed, they are either transformed or transferred from one form to another.
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6
Q

what is the law of conservation of mass?

A
  • Chemical reactions obey the law of conservation of mass.
  • In a chemical change, matter is neither created or destroyed in a reaction; they are only rearranged. Mass is conserved. (unchanged)
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7
Q

Common attributes of chemical reactions (7pt)

A
  • Bubbles of gas are formed (effervescence of odourless gas)
  • Change in appearance (state & colour)
  • A new odour may be noticed
  • The change is difficult or impossible to reverse
  • thermal or light energy is given off (or absorbed), Change in temperature
  • A sound is formed
  • Precipitation (solid formed from mixing two aqueous solutions)
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8
Q

Types of Chemical Reactions

A

there are 7
1. Combustion (burning)
2. Oxidation, Oxidation (Rusting)
3. Decomposition (Thermal / Electrolysis)
4. Precipitation
5. Neutralisation
6. Respiration
7. Photosynthesis

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9
Q

Types of Chemical Reactions
1. Combustion (aka burning)

A
  1. Combustion (aka burning)
    * Involves oxygen as reactant and release of energy (usually thermal)
    - e.g. carbon + oxygen → carbon dioxide
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10
Q

Types of Chemical Reactions
2. Oxidation + (Rusting)

A
  1. Oxidation
    * Oxidation is the addition of oxygen to a substance.
    - e.g. carbon + oxygen → carbon dioxide
    - e.g. magnesium + oxygen → magnesium oxide
  • Oxidation (Rusting)
  • Oxidation is the addition of oxygen to a substance.
  • e.g. iron + oxygen + water → hydrated iron (III) oxide (reddish-brown solid)
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11
Q

Types of Chemical Reactions
3. Decomposition (Thermal + Electroylsis)

A
  1. Decomposition (Thermal)
    * Involves breakdown of a compound into simpler substances.
    * Involves strong heating
    - e.g. sugar → carbon + water vapour
  • Decomposition (Electroylsis)
  • Involves breakdown of a compound into simpler substances
  • Involves passing electricity
  • e.g. lead bromide → lead + bromine
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12
Q

Types of Chemical Reactions
4. Precipitation

A
  1. Precipitation
    * Involves the formation of a solid when two solutions are mixed.
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13
Q

Types of Chemical Reactions
5. Neutralisation

A
  1. Neutralisation
    * The reaction of an acid and alkali to form a new substance.
    - e.g. acid + alkali → salt + water
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14
Q

Types of Chemical Reactions
6. Respiration

A
  1. Respiration
    * process by which the cells in living organisms get energy.
    - e.g. glucose + oxygen → carbon dioxide + water
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15
Q

Types of Chemical Reactions
7. Photosynthesis

A
  1. Photosynthesis
    * Process by which green plants transform light energy into chemical energy.
    - carbon dioxide + water → glucose + oxygen
    (chlorophyll & light required)
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16
Q

Acidity and Alkalinity of a Solution - 3 pts

A
  • Solutions with pH values that are less than 7 are acidic.
  • The lower the pH value, the more acidic the solution.
  • For example, the pH of milk is approximately 6.5, while the pH of vinegar (ethanoic acid) is 2.
  • Solutions with pH values that are greater than 7 are alkaline.
  • The greater the pH value, the more alkaline the solution.
  • For example, the pH of baking soda is approximately 9.5, while the pH of oven cleaner is 13.5
  • Substances which are very acidic or alkaline are usually corrosive and can burn our skin.
  • If a solution is neither acidic nor alkaline, we say that it has a neutral pH or a pH of 7 (Green universal indicator).
  • The pH of pure water is 7.
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17
Q

How to test for Universal Indicators

A
  • Litmus Paper
  • pH Scale
  • Natural Indicators
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18
Q

PH Scale (2pt)

A
  • We can use the pH scale to measure how acidic or alkaline a solution is. The values of the pH scale range from 0 to 14.
  • How to write observation: “Green universal indicator turned (colour)/remained green”
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19
Q

Litmus Paper (1 main pt, 3 opt pt)

A
  • In the school laboratory, litmus paper is often used to test whether a solution is acidic or alkaline.
  • An acidic solution turns blue litmus paper red. It has no effect on red litmus paper.
  • An alkaline solution turns red litmus paper blue. It has no effect on blue litmus paper.
  • A neutral solution has no effect on red and blue litmus paper.
  • Red litmus paper = acidic, Blue litmus paper = alkaline (follows pH scale colours)
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20
Q

Natural Indicators

A

Natural Indicators
* We can find pH indicators in nature too. They are called natural indicators. Many of these natural indicators can be prepared using plants.

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21
Q

Atomic Structure and Chemical Reaction (read lol)

A
  • The number of valence electrons elements possess determines the type of chemical reactions the elements undergo, the type of bonding they formed and their reactivity.
  • Why only valence electrons involved in chemical reactions - Valence electrons are further away from the nucleus as compared to electrons from inner electron shells. Therefore, valence electrons experience lesser force of attraction from the protons in the nucleus.
  • In the modern Periodic Table, elements are arranged according to their proton number / atomic number.
  • Atoms of elements in the same group in the Periodic Table have the same number of valence electrons (except for helium).
  • Elements in the same group have similar chemical properties and will undergo the same type of chemical reactions.
  • Atoms of elements in the same period in the Periodic Table have the same number of electron shells.
  • Across the period, the properties of elements change from metallic to non-metallic.
  • Group = vertical row, Period = horizontal row
  • The number of electrons = number of protons (which means that atomic/proton number = no. of electrons)
  • Positively charged = net change >0
  • Electrically neutral = net charge = 0
  • Negatively charged = net charge <0
  • Each electron shell can hold a certain maximum number of electrons.
  • 1st electron shell - 2 electrons
  • 2nd electron shell - 8 electrons
  • 3rd electron shell - 8 electrons (1st 20 elements only)
  • Atoms with a complete (fully occupied) valence shell are stable. They will not undergo chemical reaction under normal conditions.
  • E.g. noble gases. (18th group)
  • Note: Hydrogen, Nitrogen, Oxygen and group 17 elements exist as diatomic molecules! (i.e. they have 2 molecules)
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22
Q

Ionic Compounds & Ionic Bonding

A
  • The noble gases are elements in Group 18 of the periodic table.
  • Elements in Group 18 are monatomic because they have full valence shells and are said to have a noble gas electronic configuration.
  • Each noble gas has eight valence electrons (octet electronic configuration) except helium, which has two (duplet electronic configuration).
  • Since noble gases are stable, other atoms will bond together to achieve a noble gas electronic configuration.
  • During the collision, the valence electrons of the colliding atoms interact with atoms of a different element to found compounds.
  • Ionic bond is the electrostatic force of attraction between oppositely charged ions.
  • It is formed when the metal atom transfer valence electron/s to the non-metal atom.
  • Metallic atoms usually have 1 to 3 valence electrons while non-metallic atoms usually have 4 to 8 valence electrons.
  • An ion is a charged particle that is formed when an atom gains or loses electrons.
  • Metal ions are called cations - Metal atoms tend to lose electrons and form positive ions.
  • Non-metal ions are called anions - Most non-metal atoms will gain electrons and form negative ions.
  • When number of protons = number of electrons → neutral (atomic number = number of protons and electrons)
  • When number of protons > number of electrons → positively charged → positive ion → cation (usually metals)
  • When number of electrons > number of protons → negatively charged → negative ion → anion (usually non-metals)
  • “(name) atom gain/lose electrons to form …”
  • Ionic bonding only happens between a metal and non-metal atom!
  • The metal electron should not have any valence electrons left so if you cant fit all the valence electrons in the non-metal ion, then add more metal/non-metal atom until both have full valence electron shell! (same for non-metal electron)
  • The substance usually changes name after ionic bonding (usually only the non-metal changes name).
  • To name the ions of Group 17 elements, we change the ending of the ion’s name from -ine to -ide.
  • e.g. Fluorine → Fluoride, Chlorine → Chloride, Oxygen → Oxide, Nitrogen → Nitride, Hydrogen → Hydride, Sulfur → Sulfide
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23
Q

what is an ion?, metal non metal ions name

A
  • An ion is a charged particle that is formed when an atom gains or loses electrons.
  • Metal ions are called cations - Metal atoms tend to lose electrons and form positive ions.
  • Non-metal ions are called anions - Most non-metal atoms will gain electrons and form negative ions.
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24
Q

what is ionic bond?

A
  • Ionic bond is the electrostatic force of attraction between oppositely charged ions.
  • It is formed when the metal atom transfer valence electron/s to the non-metal atom.
  • Metallic atoms usually have 1 to 3 valence electrons while non-metallic atoms usually have 4 to 8 valence electrons.
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25
Q

meaning of positively//negatively/neutral charge?

A
  • When number of protons = number of electrons → neutral (atomic number = number of protons and electrons)
  • When number of protons > number of electrons → positively charged → positive ion → cation (usually metals)
  • When number of electrons > number of protons → negatively charged → negative ion → anion (usually non-metals)
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26
Q

notes for ionic bonding (5pt)

A
  • “(name) atom gain/lose electrons to form …”
  • Ionic bonding only happens between a metal and non-metal atom!
  • The metal electron should not have any valence electrons left so if you cant fit all the valence electrons in the non-metal ion, then add more metal/non-metal atom until both have full valence electron shell! (same for non-metal electron)
  • The substance usually changes name after ionic bonding (usually only the non-metal changes name).
  • To name the ions of Group 17 elements, we change the ending of the ion’s name from -ine to -ide.
  • e.g. Fluorine → Fluoride, Chlorine → Chloride, Oxygen → Oxide, Nitrogen → Nitride, Hydrogen → Hydride, Sulfur → Sulfide
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27
Q

Chemical Naming + Chemical Formulae (3pt each)

A
  • “(name) atom gain/lose electrons to form …”
  • Ionic bonding only happens between a metal and non-metal atom!
  • The metal electron should not have any valence electrons left so if you cant fit all the valence electrons in the non-metal ion, then add more metal/non-metal atom until both have full valence electron shell! (same for non-metal electron)
  • The substance usually changes name after ionic bonding (usually only the non-metal changes name).
  • To name the ions of Group 17 elements, we change the ending of the ion’s name from -ine to -ide.
  • e.g. Fluorine → Fluoride, Chlorine → Chloride, Oxygen → Oxide, Nitrogen → Nitride, Hydrogen → Hydride, Sulfur → Sulfide
  • Chemical Naming
  • Name the cation (metal) first followed by the anion (non-metal)
  • Indicate the ionic charge of the cation using roman numerals placed in brackets after the cation (this applies for most metals in the transition elements – only copper (II), iron (II) and iron (III) tested!
  • E.g. Calcium Oxide, Iron (II) Fluoride
  • Chemical Formulae
  • The formula of the cation is written first followed by that of the anion.
  • The total positive and negative charges must be balanced.
  • If a polyatomic ion (e.g. Zn(NO3)2) occurs more than once in the formula, it must be enclosed in brackets
28
Q

Success criteria in drawing ‘dot-and-cross’ diagram for ionic compound:

A

Success criteria in drawing ‘dot-and-cross’ diagram for ionic compound:
1. cations drawn first, followed by anions
2. use of dots () and crosses () to represent electrons from different elements (usually dots () for metal ion, crosses () for non-metal ion)
3. charges of ions (with +/- sign) written on top right-hand corner of each ion and enclosed outside square brackets.
4. number of each ion written in front as coefficient, ensuring total positive charges = total negative charges

  • only formation of ionic bonds between metals and non-metals (NaCl, MgCl2 or other binary ionic compounds with ratio of cation to anion in either 1:1, 2:1 or 1:2) tested!
29
Q

Covalent Compounds & Covalent Bonding (4-5 pt)

A
  • Covalent bonding is the electrostatic force of attraction between the shared pair of electrons and the positive nuclei of the two atoms.
  • It is formed when non-metal atoms share electrons. (sharing electrons)
  • The shared electrons are localised between the two nuclei.
  • Generally, covalent bonds are formed between atoms of non-metals.
  • Covalent bonds can be formed between atoms of the same elements or between atoms of different elements.
  • Neither atom has an ionic charge (neutral).
  • A compound whose atoms are held together by covalent bonds is a covalent compound.
  • A molecule is an uncharged group of two or more atoms held together by covalent bonds.
30
Q

meaning of covalent bonding?

A
  • Covalent bonding is the electrostatic force of attraction between the shared pair of electrons and the positive nuclei of the two atoms.
31
Q

Types of Covalent Bonds

A
  • Single covalent bond - One pair of shared electrons between two atoms (e.g. H - H)
  • Double covalent bond - Two pair of shared electrons between two atoms (e.g. O = O) (Enrichment)
  • Triple covalent bond - Three pair of shared electrons between two atoms (e.g. N ≡ N) (Enrichment)
32
Q

Nomenclature and Chemical Formulae for Covalent Compounds (prefix, 2pt)

A

Prefix / Number of atoms / Example / Name
mono- 1 NO Nitrogen monoxide
di- 2 CO2 Carbon dioxide
tri- 3 SO3 Sulfur trioxide

  • If the covalent molecule contains only one atom of the 1st element given in the formula, the prefix mono- is omitted.
  • CO carbon monoxide
  • NO2 nitrogen dioxide
  • SO2 sulfur dioxide
  • SO3 sulfur trioxide
  • The above rule does not apply for covalent compounds containing hydrogen atom.
  • e.g. H2O – water, NH3 – ammonia, HCl - hydrogen chloride
33
Q

Covalent bonding – Dot and Cross Diagram (2pt)

A
  • To differentiate the two electrons, the electron of one atom is represented by a ‘cross (x)’ while the other electron of another atom is represented by a ‘dot (*) ’.
  • For covalent compound, structural formula is also used to show the shared pair of electrons between atoms. E.g. Structural formula of hydrogen molecule is H – H. [The solid line “─” represents 2 shared electrons or a pair of shared electrons.] (enrichment).
34
Q

Guide to Writing Good Observations - adding solutions

A

Type of Procedure
Adding solutions

Recording Observation
(i) colour of precipitate

(ii) colour change in solution

Examples
(i) A ……… (colour) ppt is formed.

(ii) ………… (initial colour) solution turned ………… (final colour).

35
Q

Guide to Writing Good Observations - test for gas

A

Type of Procedure
Test for gas

Recording Observation
* Effervescence
* Colour of gas
* Smell of gas
* Specific test for gas

Examples
Effervescence of colourless and odourless gas is observed. Gas formed white ppt when bubbled into limewater.

36
Q

Guide to Writing Good Observations - Heating of solid

A

Type of Procedure
Heating of solid

Recording Observation
(i) change in colour of solid
(before and after heating)

(ii) change of state

(iii) colour of residue on cooling (may be different when hot)

Examples
(i) The green powder decomposes to form a black solid.

(ii) Solid Y melts to form a yellow liquid (not solution).

(iii) A white residue remains.

37
Q

Guide to Writing Good Observations - Adding solid to solutions

A

Type of Procedure
Adding solid to solutions

Recording Observation
* solubility of solid in water
* colour of the solution formed

Examples
……….. (colour) solid dissolves to form a ………….. (colour) solution.
OR
……….. (colour) solid remained insoluble.

38
Q

Guide to Writing Good Observations - Using Universal Indicator

A

Type of Procedure
Using Universal Indicator

Recording Observation
colour change of Universal Indicator

Examples
Green Universal Indicator turns ………… (final colour).

39
Q

Guide to Writing Good Observations - notes (3pt)

A

Notes:
* If there is no reaction, simply record “No visible change”.
* Limewater (calcium hydroxide solution) is used to test for the presence of carbon dioxide gas.
* Observation must be targeted towards product formed = don’t talk about other observation not needed or related to the product

40
Q

how to test for CO2?

A

Bubble gas into limewater, a white precipitate will form if CO2 is present

41
Q

how to test for hydrogen gas?

A

Hold lighted splint near edge of tube, if hydrogen is present, the splint will extinguish with a ‘pop’ sound

42
Q

Acids, Alkalis and salt
Acids (2-3pt)

A
  • An acid is a substance that produces hydrogen ion, H+ when it dissolves in water. (not tested)
  • The acid is given a name which ends in -ic.
  • Polyatomic ions are present in most of the acids.
  • E.g. sulfate ion (SO42-), nitrate ion (NO3-)
  • Acids have a pH level of 0-6 (0 being the most acidic).
  • Hydrochloric acid, sulfuric acid and nitric acid are strong acids and they are corrosive.

Name of Acid
Chemical Formulae

Hydrochloric Acid
HCl

Sulfuric Acid
H2SO4

Nitric Acid
HNO3

43
Q

Chemical Properties of Acids (3 pts + equation)

A
  1. Acids react with reactive metals to produce salt and hydrogen gas.
    * acid + reactive metal → salt + hydrogen gas (H2)
    - e.g. hydrochloric acid + magnesium → magnesium chloride + hydrogen gas
  2. Acids react with carbonates to produce salt, carbon dioxide gas and water.
    * acid + carbonate → salt + carbon dioxide (CO2) + water (H2O)
    - e.g. Hydrochloric acid + calcium carbonate → calcium chloride + carbon dioxide + water
  3. Acids react with alkalis (neutralisation) to produce salt and water.
    * acid + alkali → salt + water (H2O)
    - e.g. hydrochloric acid + sodium hydroxide → sodium chloride + water
  • the salt usually is the leftovers from the reactants!!
    use criss cross method to find the no. of atoms
    grp
    1 2 13 14 15 16 17 18
    charge
    1+ 2+ 3+ 4+ 3- 2- 1- 0
44
Q
  1. Acids react with reactive metals to produce ?
A
  1. Acids react with reactive metals to produce salt and hydrogen gas.
    * acid + reactive metal → salt + hydrogen gas
45
Q
  1. Acids react with carbonates to produce ?
A
  1. Acids react with carbonates to produce salt, carbon dioxide gas and water.
    * acid + carbonate → salt + carbon dioxide + water
46
Q
  1. Acids react with alkalis to produce ? what is this process called?
A
  1. Acids react with alkalis (neutralisation) to produce salt and water.
    * acid + alkali → salt + water
47
Q

Alkalis (2pt)

A
  • An alkali is a substance that produces hydroxide ion, OH- when it dissolves in water. (not tested)
  • Alkalis have a pH level of 8-14 (14 being the most alkaline).
  • Sodium hydroxide and potassium hydroxide are strong alkalis and they are corrosive.
  • Alkalis react with acids (neutralisation) to produce salt and water.
  • acid + alkali → salt + water
  • e.g. hydrochloric acid + sodium hydroxide → sodium chloride + water

Name of Alkaline
Chemical Formulae
Sodium Hydroxide
NaOH

Potassium Hydroxide
KOH

Calcium Hydroxide
Ca(OH)2

48
Q
  • Alkalis react with acids to produce ? what is this process called?
A
  • Alkalis react with acids (neutralisation) to produce salt and water.
  • acid + alkali → salt + water
49
Q

Salts (1pt) - what is a common salt usually made of?

A
  • A common salt consists of a positively charged ion (cation) [except hydrogen ion] and a negatively charged ion (anion) [except oxide and hydroxide].
  • E.g. sodium chloride, calcium fluoride
50
Q

Chemical names and chemical formulae for salts containing polyatomic ions (4pt)

A

Chemical names and chemical formulae for salts containing polyatomic ions
1. The names of the polyatomic ions take an ending -ate.
- sulfate SO42- from sulfuric acid;
- nitrate NO3- from nitric acid;

  1. The formulae of the polyatomic ions are commonly written as a group in brackets if more than one such ion is present.
    - calcium nitrate is written as Ca(NO3)2 instead of CaN2O6.
    - aluminium nitrate is written as Al(NO3)3 instead of AlN3O9.
  2. The name of the metal is followed by the name of the polyatomic ion.
    - NaNO3 sodium nitrate
    - Al2(SO4)3 aluminium sulfate
  3. For metals with more than one ionic charge, roman numerals are included in the name to indicate the charge carries by the metal.
    - Fe(NO3)2 iron(II) nitrate
    - Fe(NO3)3 iron(III) nitrate
    - CuSO4 copper(II) sulfate
51
Q

Chemical names and chemical formulae for salts containing polyatomic ions
1. The names of the polyatomic ions usually end with ?

A
  1. The names of the polyatomic ions take an ending -ate.
    - sulfate SO42- from sulfuric acid;
    - nitrate NO3- from nitric acid;
52
Q

Chemical names and chemical formulae for salts containing polyatomic ions
2. The formulae of the polyatomic ions are commonly written as ( ? ) if more than one such ion is present.

A
  1. The formulae of the polyatomic ions are commonly written as a group in brackets if more than one such ion is present.
    - calcium nitrate is written as Ca(NO3)2 instead of CaN2O6.
    - aluminium nitrate is written as Al(NO3)3 instead of AlN3O9.
53
Q

Chemical names and chemical formulae for salts containing polyatomic ions

  1. The name of the metal is followed by the name of the ( ? ).
A
  1. The name of the metal is followed by the name of the polyatomic ion.
    - NaNO3 sodium nitrate
    - Al2(SO4)3 aluminium sulfate
54
Q

Chemical names and chemical formulae for salts containing polyatomic ions

  1. For metals with more than one ionic charge, ( ? ) are included in the name to indicate the charge carries by the metal.
A
  1. For metals with more than one ionic charge, roman numerals are included in the name to indicate the charge carries by the metal.
    - Fe(NO3)2 iron(II) nitrate
    - Fe(NO3)3 iron(III) nitrate
    - CuSO4 copper(II) sulfate
55
Q

Collection and Drying of Gases
Collection of Gas
Collection methods

A

Collection Method
Solubility of Gas in Water
Density of Gas
Examples

Water Displacement
insoluble to slightly soluble
density does not affect gas collection hydrogen, oxygen, carbon dioxide

Downward Delivery
can be insoluble or soluble
denser than air
chlorine, hydrogen
chloride, sulfur dioxide

Upward Delivery
can be insoluble or soluble
less dense than
air
ammonia

56
Q

Collection and Drying of Gases
Collection of Gas

Water Displacement Method
Solubility of Gas in Water
Density of Gas
Examples

A

Water Displacement
insoluble to slightly soluble
density does not affect gas collection hydrogen, oxygen, carbon dioxide

57
Q

Collection and Drying of Gases
Collection of Gas

Downward Delivery Method
Solubility of Gas in Water
Density of Gas
Examples

A

Downward Delivery
can be insoluble or soluble
denser than air
chlorine, hydrogen
chloride, sulfur dioxide

58
Q

Collection and Drying of Gases
Collection of Gas

Upward Delivery Method
Solubility of Gas in Water
Density of Gas
Examples

A

Upward Delivery
can be insoluble or soluble
less dense than
air
ammonia

59
Q

Collection and Drying of Gases
Collection of Gas (3-4 pt optional?)

A
  • The methods used for gas collection are dependent on the physical properties of the gas, such as its solubility and density.
  • The downward and upward delivery method uses the displacement of air to collect the gas.
  • For example, gases that are denser than air will displace the air at the bottom of the gas jar.
  • To determine the density of a gas relative to the density of air, you can compare the relative molecular mass (Mr) of the gas to that of air (Mr ≈ 30).
  • If the gas has a relative molecular mass greater than 30, the gas will displace the air at the bottom of the gas jar using the downward delivery method.
60
Q

Drying Of Gas

Drying Agent
Examples
Notes

A

concentrated sulfuric acid
most gases
The gas must not react with sulfuric acid (e.g. ammonia)

quicklime (calcium oxide)
ammonia
The gas must not react with calcium oxide (e.g. carbon dioxide).

Calcium oxide must be freshly heated before use as it absorbs moisture and carbon dioxide from the air.

fused calcium chloride
hydrogen, nitrogen, carbon dioxide
The gas must not react with calcium chloride (e.g. ammonia).

Calcium chloride must be freshly heated before use as it readily absorbs moisture and carbon dioxide from the air.

61
Q

Drying Of Gas

Concentrated Sulfuric Acid
Examples
Notes

A

concentrated sulfuric acid
most gases
The gas must not react with sulfuric acid (e.g. ammonia)

62
Q

Drying Of Gas

Quicklime (calcium oxide)
Examples
Notes

A

quicklime (calcium oxide)
ammonia
The gas must not react with calcium oxide (e.g. carbon dioxide).

Calcium oxide must be freshly heated before use as it absorbs moisture and carbon dioxide from the air.

63
Q

Drying Of Gas

fused calcium chloride
Examples
Notes

A

fused calcium chloride
hydrogen, nitrogen, carbon dioxide
The gas must not react with calcium chloride (e.g. ammonia).

Calcium chloride must be freshly heated before use as it readily absorbs moisture and carbon dioxide from the air.

64
Q

Measuring the Rate of a Chemical Reaction (4pt)

A

Measuring the Rate of a Chemical Reaction

  • The rate of a chemical reaction can be determined by measuring any property that changes over the course of the reaction.
  • Common methods include measuring mass or volume changes when a gas is evolved.
  • A graph of the property against time is then plotted.
  • The rate of a chemical reaction usually decreases with time as the reactants are progressively used up.
  • The rate of reaction of hydrochloric acid with calcium carbonate can be determined using the gas syringe method.
  • We can collect the gas using a graduated gas syringe and measure the volume of gas produced over time.
65
Q
A

science (21 decks)

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