2.1.3 Amount of substance Flashcards
(145 cards)
1
Q
relative atomic mass definition
A
the weighted mean mass of an atom relative to 1/12th the mass of one atom of carbon 12
2
Q
what form will the compound be if asked to calculate the relative formula mass
A
giant ionic
giant covalent
giant metallic
3
Q
what form will the compound be if asked to calculate the relative molecular mass
A
simple molecular (covalent)
4
Q
percentage of an element equation
A
no. of atoms of the element x RAM of element
——————————————————————- X100
relative formula mass of compound
5
Q
definition of molar mass
A
the mass per mole of a substance in g/mol^-1
6
Q
amount of substance definition
A
chemists use amount of substance as a means of counting the number of particles in a substance. Its unit is the mole (mol)
7
Q
give Avogadro’s constant
A
6.02 x 10^23
8
Q
equation for the number of atoms/ions/molecules
A
moles x Avogadro’s constant
9
Q
equation for number of moles
A
mass
—————–
molar mass
10
Q
steps for empirical formula calculation
A
- find the mass of each element/ compound
- calculate moles of each (do not round till the end)
- divide the number of moles by the smallest number to get a ratio
- adjust the ratio to make the moles whole numbers
- you can then write the empirical formula
11
Q
definition for water of crystallisation
A
water molecules that are bonded into a crystallisation structure of a compound
12
Q
definition of hydrated
A
a crystallised compound containing water molecules
13
Q
word equation of the water of crystallisation of hydrated copper sulphate
A
heat
hydrated copper sulphate (blue) —-> anhydrous copper sulphate (white) + water
14
Q
symbol equation of the water of crystallisation of hydrated copper sulphate
A
CuSO4 . 5H2O —> CuSO4 . 5H2O
15
Q
definition of anhydrous
A
contains no waters of crystallisation
16
Q
method for calculating the amount of water in water of crystallisation
A
- weigh crucible
- add a known amount of hydrated salt
- weigh the crucible and hydrated salt together
- heat the hydrated salt strongly for a few minutes
- weigh and heat the sample until the mass stays constant
17
Q
what are the assumptions of the water of crystallisation practical
A
- assuming all the water has been lost by heating to constant mass
- when heat the salt is not breaking down further into other compounds
18
Q
molar gas volume definition
A
the volume per mole of gas molecules at the stated temperature and pressure (RTP)
19
Q
what is the standard room temperature and pressure
A
25 degrees celsius
101KPa pressure
20
Q
moles with dm3 gas volume equation
A
volume (dm3)
——————-
24
21
Q
moles with cm3 gas volume equation
A
volume cm3
——————
24,000
22
Q
the ideal gas volume equation
A
pressure x vol = mols x ideal gas constant x temperature
23
Q
what is temperature measured in the ideal gas equation
A
Kelvin
24
Q
how do you covert from celsius to kelvin?
A
add 273 to answer
25
how to covert from KPa to Pa
times answer by x10^3
26
how to covert answer from cm3 to m3
x10^-6
27
how to convert from dm3 to m3
x10^-3
28
what is the method for the ideal gas equation calculation question?
1. convert all units
2. rearrange equation to workout the unknown
29
stoichiometry definition
the ratio of the amount in moles of each substance in a chemical reaction
30
steps for stoichiometry calculation
1. state mr for all substances
2. workout moles for known substance
3. use ratio to find moles of the unknown
4. workout the question e.g. vol of gas or mass of substance
31
steps for limiting reactant calculation
1. workout the moles for both reactants
2. ratio - how much of each reactant you need
3. identify the limiting reactant
4. use the limiting reactants mols to workout the rest of the question
32
what is concentration measured in?
mol dm^-3
33
moles equation (conc and vol)
mols = conc x vol
—————
100
34
what is volume measured in?
cm^3
35
what is the equation for concentration?
mols x 1000
—————-
volume
36
how do you convert from mol dm^-3 to g dm^-3?
times by the Mr
37
what is the equation for percentage yield?
actual moles
———————— X100
theoretical moles
38
what is the definition of percentage yield?
the amount of product made from the starting materials
39
what are the steps for a percentage yield calculation?
1 - workout the Mr of the reactants and products that you have a mass for
2 - workout the actual moles (moles of product)
3 - workout the theoretical moles (moles of the reactant THEN RATIO)
4 - put moles back into equation
40
what is the equation for atom economy?
sum of molar masses of desired
——————————————— X100
sum of molar masses of all products
41
what is the atom economy if a reaction only has one product?
100%
42
which is the only calculation where you use the big number infront of the element?
ATOM ECONOMY
43
how many kg are in a tonne?
1000
44
what is the definition for empirical formula?
the simplest ratio of atoms of each element in a compound
45
what is the definition of a mole?
the amount of any substance containing as many particles as there are carbon atoms in 12g of carbon 12
46
what is the definition of hydrated?
a crystallised compound containing water molecules
47
what is the definition of Avogadro's constant?
6.02x10^23 the number of carbon atoms in a mole of carbon 12
48
what is the definition for molecular formula?
the actual number of atoms of each element in the compound
49
What is the definition of a mole?
The mole is the amount of substance in grams that has the same number of particles as there are atoms in 12 grams of carbon-12.
50
Define relative atomic mass.
Relative atomic mass is the average mass of one atom compared to one twelfth of the mass of one atom of carbon-12.
51
What is molar mass?
Molar mass is the mass in grams of 1 mole of a substance, given in the unit g mol-1.
52
How is molar mass calculated for a compound?
Molar mass for a compound is calculated by adding up the mass numbers of each element in the compound.
53
What is the molar gas volume at room temperature and pressure?
At room pressure (1 atm) and room temperature (25°C), the molar gas volume is 24 dm³ mol-1.
54
What is Avogadro's constant?
Avogadro's constant is 6.02 x 10^23, which indicates the number of atoms in 12 grams of carbon-12.
55
True or False: 1 mole of any specified entity contains 6.02 x 10^23 of that entity.
True.
56
What is the unit of mass used in amount calculations?
Grams.
57
Fill in the blank: 1000 mg = _______.
1 g.
58
What is the definition of an empirical formula?
An empirical formula is the simplest ratio of atoms of each element in the compound.
59
List the steps to calculate an empirical formula.
* Divide each mass (or % mass) by the atomic mass of the element
* Divide each of the answers by the smallest one of those numbers
* Multiply to give whole numbers if needed.
60
What is the definition of a molecular formula?
A molecular formula is the actual number of atoms of each element in the compound.
61
How do you determine the molecular formula from the empirical formula?
From the relative molecular mass (Mr), work out how many times the mass of the empirical formula fits into the Mr.
62
Example: What is the molecular formula for a compound with an empirical formula of C3H6O and a Mr of 116?
C6H12O2.
63
What is a hydrated salt?
A hydrated salt contains water of crystallisation
## Footnote
Example: Cu(NO3)2 - 6H2O is hydrated copper (II) nitrate(V).
64
What is the formula for anhydrous copper (II) nitrate(V)?
Cu(NO3)2
## Footnote
Anhydrous means it does not contain water.
65
What is the method for measuring mass loss in thermal decomposition reactions?
Heating in a crucible
## Footnote
This method measures mass loss or gain during reactions.
66
What happens to the water of crystallisation in calcium sulfate when heated?
It is removed as water vapour
## Footnote
Example equation: CaSO4·xH2O(s) → CaSO4(s) + xH2O(g).
67
What is the first step in the method of heating a hydrated salt in a crucible?
Weigh an empty clean dry crucible and lid
## Footnote
This ensures accurate measurement of mass loss.
68
What is the significance of using a lid on the crucible during heating?
It prevents loss of solid from the crucible
## Footnote
The lid should be loose to allow gas escape.
69
What mass of hydrated calcium sulfate is recommended for accurate results?
Use no more than 2g
## Footnote
Large amounts, like 50g, may lead to incomplete decomposition.
70
What is a solution in chemistry?
A mixture formed when a solute dissolves in a solvent
## Footnote
Water is the most common solvent for aqueous solutions.
71
How is molar concentration calculated?
Molar concentration = amount in moles of solute / volume of solution
## Footnote
The unit is mol dm⁻³ or M.
72
What is the unit of volume used in molar concentration calculations?
dm³
## Footnote
1 dm³ = 1 litre.
73
Convert 1 m³ to dm³.
1 m³ = 1000 dm³
## Footnote
1 m³ is a cube of 100 cm on each side.
74
How do you convert cm³ to dm³?
Divide by 1000
## Footnote
1 cm³ = 1 mL.
75
What is the formula for mass concentration?
mass concentration = mass / volume
76
How do you convert concentration from mol dm³ to g dm³?
conc in g dm-3 = conc in mol dm-3 x Mr
77
What is the unit of mass concentration?
g dm-3
78
What happens when soluble ionic solids dissolve in water?
They dissociate into separate ions.
79
What are the concentrations of sodium ions and chloride ions when 0.1 mol of sodium chloride is dissolved?
* Sodium ions: 0.1 mol dm-3
* Chloride ions: 0.1 mol dm-3
80
What is the concentration of magnesium ions and chloride ions when 9.53g of magnesium chloride (MgCl₂) is dissolved in 1 dm³ of water?
* Magnesium ions: 0.1 mol dm-3
* Chloride ions: 0.2 mol dm-3
81
What is the first step in making a solution?
Weigh the sample bottle containing the required mass of solid on a 2 dp balance.
82
What should be done if the substance does not dissolve well in cold water?
Heat the beaker and its contents gently until all the solid has dissolved.
83
How should you ensure a uniform solution after making it?
Invert the flask several times.
84
When diluting a solution, what remains constant?
The amount of moles of solute present.
85
What is the formula for calculating dilutions?
Original volume x original concentration = new diluted volume x new diluted concentration
86
What is the new diluted concentration if 50 cm³ of water is added to 150 cm³ of a 0.20 mol dm-3 NaOH solution?
0.15 mol dm-3
87
How much water must be added to dilute 5.00 cm³ of 1.00 mol dm-3 hydrochloric acid to a concentration of 0.050 mol dm-3?
95 cm³
88
What personal protective equipment should be worn when handling dilute acids and alkalis?
Wear goggles.
89
True or False: Hazardous substances in low concentrations pose the same risks as the pure substance.
False
90
What is Avogadro's Constant?
6.02 x 10^23 particles per mole
## Footnote
This constant is used to define the number of atoms, molecules, or ions in one mole of a substance.
91
How many atoms are in 1 mole of copper?
6.02 x 10^23 atoms
## Footnote
This is a direct application of Avogadro's Constant.
92
How do you calculate the number of particles in a substance?
Number of particles = amount of substance (in mol) x Avogadro's constant
## Footnote
This formula is applicable for any specified entity.
93
What is the formula to calculate density?
Density = mass/volume
## Footnote
Density is typically expressed in g cm^-3.
94
What is the amount of substance in moles for 6.00 g of tin with Ar = 118.7?
0.05055 mol
## Footnote
This is calculated using the formula: amount = mass/Ar.
95
How many chloride ions are produced from 25.0 cm³ of 0.400 mol dm^-3 magnesium chloride?
1.204 x 10^22 ions
## Footnote
This calculation involves determining the amount of magnesium chloride and the stoichiometry of the reaction.
96
Fill in the blank: The density of ethanol is ______ g cm^-3.
0.789
97
What is the mass of ethanol in 0.500 dm³ of ethanol?
394.5 g
## Footnote
This is calculated using the density and volume: mass = density x volume.
98
What is the density of gold calculated in kg dm^-3?
19.3 kg dm^-3
## Footnote
This is determined from the mass and volume of the gold bar.
99
True or False: 1 mole of sodium ions contains 6.02 x 10^23 ions.
True
100
What is the first step in converting quantities between different substances using a balanced equation?
Convert any given quantity into amount in mol
## Footnote
This can be done using mass, volume of gas, or concentration.
101
How do you calculate the mass of carbon dioxide produced from heating sodium hydrogencarbonate?
mass = amount x Mr
## Footnote
This follows a three-step process involving the balanced equation.
102
What is the total volume of gas produced from the decomposition of 0.651 g of magnesium nitrate?
0.303 dm³
## Footnote
This requires calculating moles of magnesium nitrate and applying the ideal gas law.
103
How do you calculate the concentration of H₂SO₄ from a neutralization reaction?
Concentration = amount/volume
## Footnote
This is derived from the moles of H₂SO₄ obtained from the balanced equation.
104
What is the mass of copper that reacts with 150 cm³ of 1.60 mol dm^-3 nitric acid?
5.71 g
## Footnote
This is determined through a series of calculations involving stoichiometry.
105
What is the molecular weight (Mr) used for ethanol (C₂H₅OH)?
46.0 g/mol
106
What is the formula for calculating the amount of gas produced in a reaction?
Volume = nRT/P
## Footnote
This uses the ideal gas law where n is the number of moles, R is the gas constant, T is temperature in Kelvin, and P is pressure.
107
What is the balanced chemical equation for the reaction of titanium chloride with sodium?
TiCl + 4 Na → 4 NaCl + Ti
108
How do you calculate the amount in moles of a substance?
amount = mass / Mr
109
Calculate the moles of TiCl from 100 g given a molar mass of 189.9 g/mol.
0.527 mol
110
Calculate the moles of sodium from 80 g given a molar mass of 23.0 g/mol.
3.48 mol
111
What is the limiting reactant when reacting TiCl with sodium?
TiCl
112
If 0.527 mol of TiCl is used, how many moles of Ti are produced?
0.527 mol
113
How do you calculate the mass of titanium formed from moles?
Mass = amount x Mr
114
Calculate the mass of titanium formed from 0.527 mol given a molar mass of 47.9 g/mol.
25.24 g
115
What is the formula for calculating percentage yield?
% yield = (actual yield / theoretical yield) × 100
116
Calculate the percentage yield if 10.0 g of Fe is produced from a theoretical yield of 17.48 g.
57.2%
117
What is the formula for calculating % atom economy?
% atom economy = (mass of useful products / mass of all reactants) × 100
118
What is the % atom economy for the reaction Fe2O3 + 3 CO → 2 Fe + 3 CO2?
45.8%
119
What is an ideal reaction in terms of atom economy?
A reaction with only one product where all atoms are used, resulting in 100% atom economy.
120
What can improve the economics of a process with a side waste product?
Selling the by-product for other uses.
121
What is the charge of lithium?
+1
122
What is the formula for lithium sulfate?
Li2SO4
## Footnote
Lithium has a +1 charge and sulfate has a -2 charge, requiring two lithium ions to balance the charge.
123
What is the charge of calcium?
+2
124
What is the formula for calcium phosphate?
Ca3(PO4)2
## Footnote
Calcium has a +2 charge and phosphate has a -3 charge, requiring three calcium ions to balance two phosphate ions.
125
What are spectator ions?
Ions that do not change state or oxidation number in a reaction.
126
What is the formula for ammonium ion?
(NH4)+
127
What is the formula for sulfate ion?
(SO4)2-
128
What is the charge of phosphate?
-3
129
What is the formula for nitrate ion?
(NO3)-
130
What is the formula for carbonate ion?
(CO3)2-
131
What is the formula for hydroxide ion?
(OH)-
132
How do you write an ionic equation?
1. Separate (aq) solutions into ions 2. Cancel out spectator ions
133
True or False: Ionic equations show all ions present in a reaction.
False
134
What is the formula for copper(II) nitrate?
Cu(NO3)2
135
What is the formula for calcium hydroxide?
Ca(OH)2
136
What is the charge of zinc?
+2
137
What is the charge of iron(II)?
+2
138
What is the charge of iron(III)?
+3
139
Fill in the blank: To combine ions into a neutral compound, the total positive charge must _______ the total negative charge.
cancel out
140
List the key ions in Group 1.
* Hydrogen
* Silver
* Gold
* Ammonium (NH4)+
141
List the key ions in Group 2.
* Zinc
* Copper (II)
* Iron (II)
* Tin
* Lead
142
List the key ions in Group 3.
* Iron (III)
143
List the key ions in Group 5.
* Phosphate
144
List the key ions in Group 6.
* Carbonate (CO3)2-
* Sulfate
145
List the key ions in Group 7.
* Nitrate (NO3)-
* Hydroxide (OH)-
