Formulas Flashcards
(104 cards)
1
Q
What are the 7 elements classed as?
A
These 7 elements are classed as simple molecules.
2
Q
How do atoms combine to form molecules?
A
Atoms combine together in fixed ratios that will give them full outer shells of electrons.
3
Q
What is formed when atoms combine?
A
When this happens, a molecule is formed.
4
Q
What does the molecular formula of a molecule show?
A
The molecular formula shows the type of atoms involved and the number of atoms.
5
Q
What indicates the type of atoms in a molecular formula?
A
The type of atoms is indicated by the chemical symbol.
6
Q
What indicates the number of atoms in a molecular formula?
A
The number of atoms is indicated by the subscript (little) number after a chemical symbol.
7
Q
What is the molecular formula for Hydrogen?
A
H2
Made from 2 hydrogen atoms.
8
Q
What is the molecular formula for Chlorine?
A
Cl2
Made from 2 chlorine atoms.
9
Q
What is the molecular formula for Water?
A
H2O
Made from 2 hydrogen atoms and 1 oxygen atom.
10
Q
What is the molecular formula for Methane?
A
CH4
Made from 1 carbon atom and 4 hydrogen atoms.
11
Q
What is the molecular formula for Ammonia?
A
NH3
Made from 1 nitrogen atom and 3 hydrogen atoms.
12
Q
What is the molecular formula for Sulfuric acid?
A
H2SO4
Made from 2 hydrogen atoms, 1 sulfur atom, and 4 oxygen atoms.
13
Q
What is the overall charge of ionic compounds?
A
Ionic compounds typically have no overall charge.
14
Q
What does it mean when ionic compounds have no overall charge?
A
The size of any positively charged ion is cancelled by the size of any negatively charged ion.
15
Q
How can the formula of an ionic compound be determined?
A
The formula can be determined by directly comparing the charges of the ions.
16
Q
What is the charge of the iron(II) ion?
A
The iron(II) ion is Fe2+, which means it has a 2+ or +2 charge.
17
Q
What is the charge of the sulfate ion?
A
The sulfate ion is SO42–, which means it has a 2– or –2 charge.
18
Q
How do the charges of Fe2+ and SO42– relate to each other?
A
The charges cancel each other out: (+2) + (–2) = 0.
19
Q
What is the formula of iron(II) sulfate?
A
The formula of iron(II) sulfate is FeSO4.
20
Q
What is the swap-and-drop method?
A
It is a method used when the ions in the ionic compound have different charges.
21
Q
What should be noted when using the swap-and-drop method?
A
If you use this method with ions that have the same charge, you must give the simplest whole number ratio.
22
Q
What is the charge of the copper(II) ion?
A
The copper(II) ion is Cu2+, which means it has a 2+ or +2 charge.
23
Q
What is the charge of the chloride ion?
A
The chloride ion is Cl–, which means it has a 1– or –1 charge.
24
Q
What do word equations show?
A
Word equations show the reactants and products of a chemical reaction using their full chemical names.
25
What are reactants in a chemical reaction?
The reactants are the substances on the left-hand side of the arrow.
26
What are products in a chemical reaction?
The products are on the right-hand side of the arrow.
27
What does the arrow in a word equation imply?
The arrow implies the conversion of reactants into products.
28
What can be written above the arrow in a word equation?
Reaction conditions or the name of a catalyst can be written above the arrow.
29
What is an example of a word equation?
sodium hydroxide + hydrochloric acid ⟶ sodium chloride + water
30
What is a symbol equation?
A symbol equation uses the formulae of the reactants and products to show what happens in a chemical reaction.
31
Where should reactants and products be placed in a symbol equation?
Reactants should be on the left of the equation and products on the right.
32
Which non-metals should be written as molecules in a symbol equation?
H2, N2, O2, F2, Cl2, Br2, and I2.
33
What are the state symbols used in symbol equations?
Solid = (s), Liquid = (l), Gas = (g), Aqueous = (aq).
34
What should you consider when determining the correct state symbol?
Look for clues in the identity of substances in a reaction.
35
What is the general state of metal compounds?
Metal compounds will always be solid, although there are a few exceptions.
36
What is the usual state of ionic compounds?
Ionic compounds will usually be solids.
37
What states can non-metal compounds be in?
Non-metal compounds can be solids, liquids, or gases.
38
What do precipitates formed in solution count as?
Precipitates formed in solution count as solids.
39
What must a symbol equation be to represent the correct ratio of reactants and products?
A symbol equation must be balanced.
40
Can you provide an example of a balanced symbol equation?
S (s) + O2 (g) → SO2 (g)
## Footnote
This shows that one atom of solid sulfur reacts with one gaseous molecule of oxygen to make one gaseous molecule of sulfur dioxide.
41
What is the symbol for relative atomic mass?
The symbol for relative atomic mass is Ar.
42
Where can the relative atomic mass for each element be found?
The relative atomic mass for each element can be found in the Periodic Table, along with the atomic number.
43
How is relative atomic mass shown?
Relative atomic mass is shown on the atomic symbol.
44
Is relative atomic mass always larger than atomic number?
Relative atomic mass is always larger than the atomic number (except for hydrogen, where they are the same).
45
What is the symbol for relative molecular mass?
The symbol for the relative molecular mass is Mr.
46
What is relative molecular mass?
Relative molecular mass is the sum of the relative atomic masses of all the atoms in a molecule.
47
What does the term relative formula mass refer to?
The term relative formula mass is used when referring to the total mass of an ionic compound.
48
How do you calculate the Mr of a substance?
To calculate the Mr of a substance, you have to add up the relative atomic masses of all the atoms present in the formula.
49
What is the Mr of H2?
The Mr of H2 is 2.
## Footnote
Calculation: (2 x H) = (2 x 1) = 2
50
What is the Mr of H2O?
The Mr of H2O is 18.
## Footnote
Calculation: (2 x H) + (1 x O) = (2 x 1) + (1 x 16) = 18
51
What is the Mr of K2CO3?
The Mr of K2CO3 is 138.
## Footnote
Calculation: (2 x K) + (1 x C) + (3 x O) = (2 x 39) + (1 x 12) + (3 x 16) = 138
52
What is the Mr of Ca(OH)2?
The Mr of Ca(OH)2 is 74.
## Footnote
Calculation: (1 x Ca) + (2 x O) + (2 x H) = (1 x 40) + (2 x 16) + (2 x 1) = 74
53
What is the Mr of (NH4)2SO4?
The Mr of (NH4)2SO4 is 132.
## Footnote
Calculation: (2 x N) + (8 x H) + (1 x S) + (4 x O) = (2 x 14) + (8 x 1) + (1 x 32) + (4 x 16) = 132
54
What unit is used to measure chemical amounts?
Chemical amounts are measured in moles.
55
What is the symbol for the mole?
The mole is represented by the symbol 'mol'.
56
What does one mole of any substance contain?
One mole of any substance contains the same number of the stated particles.
57
What types of particles can one mole contain?
One mole can contain atoms, molecules, or ions.
58
How many particles are in one mole?
One mole contains 6.02 x 10^23 particles.
## Footnote
This number is known as the Avogadro constant.
59
How many atoms are in one mole of sodium (Na)?
One mole of sodium (Na) contains 6.02 x 10^23 atoms of sodium.
60
How many molecules are in one mole of hydrogen (H2)?
One mole of hydrogen (H2) contains 6.02 x 10^23 molecules of hydrogen.
61
How many formula units are in one mole of sodium chloride (NaCl)?
One mole of sodium chloride (NaCl) contains 6.02 x 10^23 formula units of sodium chloride.
62
How can the number of moles of any chemical be calculated?
The number of moles can be calculated using the formula: Moles = mass / M_r.
63
What is the formula triangle used for?
The formula triangle is used to convert between moles, mass in grams, and molar mass.
64
Triangle Linking Moles, Mass, Mr
65
What happens when one of the reactants is used up in a chemical reaction?
The chemical reaction stops.
66
What is the limiting reactant?
The reactant that is used up first, limiting the duration and amount of product that can be produced.
67
What is the excess reactant?
The reactant that remains after the limiting reactant is used up.
68
What is the limiting reagent?
The reactant which is not present in excess in a reaction.
69
How is the amount of product related to the limiting reactant?
The amount of product is directly proportional to the amount of the limiting reactant added at the beginning of a reaction.
70
How do you determine the limiting reactant?
Consider the amounts of each reactant used and the molar ratio of the balanced chemical equation.
71
What should be used in reacting mass calculations?
The limiting reagent, as it indicates the maximum possible amount of product that can form.
72
What happens once all of a limiting reagent has been used up?
The reaction cannot continue.
73
What are the steps to determine the limiting reactant?
1. Convert the mass of each reactant into moles by dividing by the molar masses.
2. Write the balanced equation and determine the molar ratio.
3. Compare the moles.
74
What is a solute?
A solute is a solid substance that dissolves into a liquid.
75
How can the amount of solute be expressed?
The amount of solute can be expressed in grams (g) or moles (mol).
76
What is a solvent?
A solvent is the liquid that a solute dissolves in.
77
How is the volume of a solvent measured?
The amount / volume of a solvent is measured in cm3 or dm3.
78
Where do most chemical reactions occur?
Most chemical reactions occur between solutes which are dissolved in solvents, such as water or an organic solvent.
79
What is a solution?
A solution is the mixture formed when a solute dissolves in a solvent.
80
How is the volume of a solution measured?
The amount / volume of a solution is measured in cm3 or dm3.
81
What does concentration refer to?
Concentration refers to the amount of solute there is in a specific volume of the solvent.
82
What happens to concentration with more solute?
The greater the amount of solute in a given volume, the greater the concentration.
83
What is concentration sometimes referred to as?
Concentration is sometimes commonly referred to as strength.
## Footnote
For example, dissolving more coffee in hot water results in a stronger coffee.
84
How is concentration typically expressed?
Typically, concentration is expressed in terms of the amount of substance per dm3.
85
What are the units of concentration?
The units of concentration are: g / dm3 and mol / dm3.
86
Concentration, Moles, Volume Triangle
87
What are the steps to calculate empirical formulae?
1. Write the element.
2. Write the value given for each element (mass in g or percentage).
3. Write the relative atomic mass of each element.
4. Calculate the moles of each element (Moles = mass / A_r).
5. Calculate the ratio of elements by dividing all moles by the smallest number of moles.
6. If necessary, multiply to get whole numbers.
7. Write the final empirical formula.
88
What is the difference between empirical and molecular formula?
The empirical formula shows the simplest ratio of elements, while the molecular formula gives the actual number of atoms of each element in the compound.
89
How do you calculate the molecular formula from the empirical formula?
1. Find the relative formula mass of the empirical formula.
2. Use the equation: (relative formula mass of molecular formula) / (relative formula mass of empirical formula).
3. Multiply the number of each element in the empirical formula by the result from step 2.
90
What are the steps to calculate water of crystallisation?
1. Write the salt and water.
2. Write the value given for the salt and water.
3. Write the relative molecular/formula mass of the salt and water.
4. Calculate the moles of the salt and water (Moles = mass / M_r).
5. Calculate the ratio of salt to water by dividing by the smallest number of moles.
6. Write the final hydrated salt formula.
91
What does percentage yield compare?
Percentage yield compares the actual yield to the theoretical yield.
92
What is the equation for percentage yield?
percentage yield = (actual yield / theoretical yield) × 100
93
What is actual yield?
Actual yield is the recorded amount of product obtained.
94
What is theoretical yield?
Theoretical yield is the amount of product that would be obtained under perfect practical and chemical conditions.
95
What typically involves a reacting mass calculation?
Typically, this involves a reacting mass calculation based on the balanced symbol equation.
96
What is percentage composition?
Percentage composition expresses the mass of each element as a percentage of the total mass of the compound.
97
What is the equation for percentage composition?
percentage composition of an element = (total mass of the element in the compound / relative formula mass of the compound) × 100
98
What is the total mass of water (H2O)?
The total mass of water is (2 × 1) + 16 = 18.
99
What is the percentage composition of hydrogen in water?
Percentage of hydrogen = (2 × 1 / 18) × 100 = 11.1%.
100
What is the percentage composition of oxygen in water?
Percentage of oxygen = (1 × 16 / 18) × 100 = 88.9%.
101
What should the total percentage by mass of all elements add up to?
The total percentage by mass of all elements should add up to 100%.
102
What defines a pure substance?
A pure substance has nothing else mixed with it.
103
What can contaminate the product you are trying to obtain?
Unwanted substances such as unreacted reactants, catalysts, and other impurities can contaminate the product.
104
What is the equation to calculate percentage purity?
percentage purity = (mass of pure substance / total mass of substance) × 100
