C3 - Quantitative Chemistry

Question 1

What is the definition of a mole?

Answer 1

A mole is simply the name given to an amount of a substance.

Question 2

What does the mass of one mole of atoms or molecules equal?

Answer 2

The mass in grams is equal to the relative atomic mass (A) or relative formula mass (M) of the element or compound.

Question 3

What is the mass of one mole of carbon?

Answer 3

12 g.

Question 4

What is the mass of one mole of nitrogen gas (N₂)?

Answer 4

28 g.

Question 5

What is the mass of one mole of carbon dioxide (CO₂)?

Answer 5

44 g.

Question 6

How many particles are contained in one mole of any substance?

Answer 6

6.023 x 10²³ atoms or molecules.

Question 7

What is the formula to calculate the number of moles in a given mass?

Answer 7

Number of moles = mass in g (of an element or compound) ÷ M (of the element or compound).

Question 8

Calculate the number of moles in 66 g of carbon dioxide (CO₂).

Answer 8

1.5 mol.

Question 9

What is the molar mass (M) of carbon dioxide (CO₂)?

Answer 9

44 g (12 + [2 x 16]).

Question 10

What is the symbol for the unit ‘moles’?

Answer 10

‘mol’.

Question 11

If there are 4 moles of carbon dioxide (CO₂), how many moles of carbon are present?

Answer 11

4 moles.

Question 12

What is the mass of carbon in 4 moles of carbon dioxide (CO₂)?

Answer 12

48 g.

Question 13

Fill in the blank: The number of moles can be rearranged using a _______ triangle.

Answer 13

formula.

Question 14

True or False: The mole is a unit that represents a specific quantity of particles.

Answer 14

True.

Question 15

What is the importance of the mole in chemistry?

Answer 15

It allows for the conversion between the mass of substances and the number of particles.

Question 16

What does the formula triangle help to find?

Answer 16

It helps to find mass, number of moles, or molar mass.

Question 17

What does ‘M’ represent in the context of moles?

Answer 17

Molar mass of the element or compound.

Question 18

What is the relationship between moles and grams in a chemical reaction?

Answer 18

The number of moles of reactants and products must be conserved.

Question 19

What is the principle regarding mass in a chemical reaction?

Answer 19

Mass is always conserved during a chemical reaction

This means no atoms are destroyed or created.

Question 20

What happens to the number and types of atoms during a chemical reaction?

Answer 20

The number and types of atoms remain the same on each side of the reaction equation.

Question 21

What does it mean when we say mass is conserved?

Answer 21

No mass is lost or gained during a chemical reaction.

Question 22

Provide an example of a balanced equation that demonstrates conservation of mass.

Answer 22

2Li + F2 → 2LiF

Question 23

How do you show that mass is conserved in the reaction 2Li + F2 → 2LiF?

Answer 23

Total mass of reactants equals total mass of products: 2 x M(Li) + 2 x M(F) = 52 and 2 x M(LiF) = 52.

Question 24

What happens to mass in an unsealed reaction vessel when a gas is involved?

Answer 24

The mass may appear to change due to gas escaping or entering the vessel.

Question 25

If the mass of a reaction vessel increases, what is one possible explanation?

Answer 25

One of the reactants is a gas found in air that enters the vessel.

Question 26

If the mass of a reaction vessel decreases, what is a likely reason?

Answer 26

One of the products is a gas that escapes into the air.

Question 27

In a thermal decomposition reaction, what is the relationship between the mass of the reactants and products?

Answer 27

The total mass of the reactants equals the total mass of the products.

Question 28

Fill in the blank: In a reaction where a metal carbonate decomposes, the equation is ______.

Answer 28

metal carbonate(s) → metal oxide(s) + carbon dioxide(g)

Question 29

True or False: A gas will expand to fill any container it's in.

Answer 29

True

Question 30

What happens to gas produced in a reaction if the reaction vessel is not sealed?

Answer 30

The gas escapes into the air around the vessel.

Question 31

What is the relative formula mass of a compound?

Answer 31

The sum of the relative atomic masses of all the atoms in the molecular formula.

Question 32

How do you find the relative formula mass of MgCl₂?

Answer 32

Mg + (2 × Cl) = 24 + (2 × 35.5) = 95.

Question 33

What is the relative atomic mass (Aᵣ) of magnesium?

Answer 33

24.

Question 34

What is the relative atomic mass (Aᵣ) of chlorine?

Answer 34

35.5.

Question 35

How do you calculate the percentage mass of an element in a compound?

Answer 35

Percentage mass = (Aᵣ × number of atoms of that element) / Mᵣ of the compound × 100.

Question 36

What is the percentage mass of sodium in sodium carbonate (Na₂CO₃)?

Answer 36

23 / 106 × 100 = 43%.

Question 37

If a mixture contains 20% iron ions by mass, how much iron is in 50 g of the mixture?

Answer 37

10 g of iron.

Question 38

What is the percentage mass of iron in iron chloride (FeCl₂)?

Answer 38

44.09%.

Question 39

How much iron chloride is needed to provide 10 g of iron?

Answer 39

23 g of iron chloride.

Question 40

Fill in the blank: The formula to calculate the percentage mass of an element in a compound is _______.

Answer 40

(Aᵣ × number of atoms) / Mᵣ × 100.

Question 41

True or False: The relative atomic mass of an element can be found on the periodic table.

Answer 41

True.

Question 42

What does the number of moles in a chemical reaction represent?

Answer 42

The number of moles indicates how many moles of each substance take part or is formed during the reaction.

Question 43

In the reaction Mg(a) + 2HC(09) → MgC| (09) + 2(8), how many moles of magnesium react?

Answer 43

1 mole of magnesium.

Question 44

In the same reaction, how many moles of hydrochloric acid are involved?

Answer 44

2 moles of hydrochloric acid.

Question 45

What is the first step to balance equations using reacting masses?

Answer 45

Divide the mass of each substance by its relative formula mass to find the number of moles.

Question 46

What should you do if the numbers of moles calculated are not whole numbers?

Answer 46

Multiply all the numbers by the same amount so that they all become whole numbers.

Question 47

How do you write the balanced symbol equation for a reaction?

Answer 47

By putting the whole number ratios in front of the chemical formulas.

Question 48

What is the relative formula mass (M) of zinc oxide (ZnO)?

Answer 48

81.

Question 49

What is the relative formula mass (M) of carbon dioxide (CO2)?

Answer 49

44.

Question 50

How many moles of carbon were produced when 0.60 g reacted?

Answer 50

0.050 mol.

Question 51

What is the balanced symbol equation for the reaction involving zinc oxide and carbon?

Answer 51

2ZnO + C → CO2 + 2Zn.

Question 52

Fill in the blank: The big numbers in front of the chemical formulas in a balanced equation indicate the number of _______.

Answer 52

[moles]

Question 53

True or False: The little numbers in chemical formulas indicate how many moles of each element are present.

Answer 53

False.

Question 54

What do you need to calculate the number of moles from the mass of a substance?

Answer 54

The relative formula mass (M) of the substance.

Question 55

List the steps to balance a chemical equation using reacting masses.

Answer 55

* Divide the mass by M * Divide by the smallest number of moles * Multiply to make whole numbers * Write the balanced equation.

Question 56

What is the relative atomic mass (A) of zinc (Zn)?

Answer 56

65.

Question 57

After calculating moles, if you get 0.10 for ZnO, what does this imply about its ratio in the balanced equation?

Answer 57

It will be in a ratio of 2 in the balanced equation.

Question 58

What is the limiting reactant?

Answer 58

The reactant that's used up in a reaction ## Footnote It limits the amount of product that's formed.

Question 59

What happens to the reaction when one reactant is used up?

Answer 59

The reaction stops ## Footnote Any remaining reactants are in excess.

Question 60

How is the amount of product formed related to the limiting reactant?

Answer 60

Directly proportional ## Footnote Halving the limiting reactant halves the product; doubling it doubles the product.

Question 61

What is the first step in calculating the mass of a product formed in a reaction?

Answer 61

Write out the balanced equation ## Footnote This is essential for stoichiometric calculations.

Question 62

What is the second step in calculating the mass of a product formed?

Answer 62

Work out relative formula masses (M.) of the reactant and product ## Footnote This helps in mole calculations.

Question 63

What formula is used to calculate the number of moles?

Answer 63

Moles = mass / molar mass ## Footnote This formula is crucial for converting mass to moles.

Question 64

In the example provided, what is the balanced equation for the reaction of aluminium?

Answer 64

4Al + 3O2 → 2Al2O3 ## Footnote This equation shows the stoichiometry of the reaction.

Question 65

What is the relative formula mass of aluminium oxide (Al2O3)?

Answer 65

102 ## Footnote Calculated as (2 × 27) + (3 × 16).

Question 66

How many moles of aluminium are in 135 g?

Answer 66

5 moles ## Footnote Calculated using the formula: Moles = 135 g / 27 g/mol.

Question 67

What is the mole ratio of aluminium to aluminium oxide in the reaction?

Answer 67

4 moles of Al react to produce 2 moles of Al2O3 ## Footnote This indicates that half the number of moles of aluminium oxide is produced.

Question 68

How many moles of aluminium oxide are produced from 5 moles of aluminium?

Answer 68

2.5 moles ## Footnote This is derived from the stoichiometric ratio in the balanced equation.

Question 69

What is the mass of 2.5 moles of aluminium oxide?

Answer 69

255 g ## Footnote Calculated using mass = moles × Molar mass (2.5 × 102).

Question 70

Fill in the blank: The amount of product formed is directly proportional to the amount of _______.

Answer 70

[limiting reactant]

Question 71

True or False: Excess reactants are completely consumed in a reaction.

Answer 71

False ## Footnote Excess reactants remain after the limiting reactant is used up.

Question 72

What is concentration in the context of solutions?

Answer 72

The amount of a substance (e.g., mass or number of moles) in a certain volume of a solution ## Footnote Concentration indicates how crowded the solute is in a solution.

Question 73

What happens to the concentration of a solution as more solute is added?

Answer 73

The concentration increases ## Footnote More solute means more crowded conditions in the solution.

Question 74

How is concentration measured in g/dm³?

Answer 74

Concentration = mass of solute / volume of solvent in dm³ ## Footnote Units are expressed as grams per cubic decimeter.

Question 75

Calculate the concentration of a sodium chloride solution with 30 g dissolved in 0.2 dm³ of water.

Answer 75

150 g/dm³ ## Footnote Calculation: 30 g / 0.2 dm³ = 150 g/dm³.

Question 76

Convert 500 cm³ to dm³.

Answer 76

0.5 dm³ ## Footnote 500 cm³ ÷ 1000 = 0.5 dm³.

Question 77

What is the concentration of a solution with 15 g of salt in 500 cm³?

Answer 77

30 g/dm³ ## Footnote Calculation: Concentration = 15 g / 0.5 dm³ = 30 g/dm³.

Question 78

How do you rearrange the formula for concentration to find mass?

Answer 78

mass = concentration x volume ## Footnote This formula allows you to calculate the mass of solute needed.

Question 79

What mass of salt is needed to achieve a concentration of 24 g/dm³ in 0.40 dm³ of water?

Answer 79

9.6 g ## Footnote Calculation: mass = 24 g/dm³ x 0.40 dm³ = 9.6 g.

Question 80

Fill in the blank: Concentration can be measured in _______.

Answer 80

g/dm³ ## Footnote This is a common unit for measuring concentration in solutions.

Question 81

True or False: The concentration of a solution decreases as more solute is added.

Answer 81

False ## Footnote More solute increases the concentration of the solution.

Question 82

What is the formula to calculate concentration?

Answer 82

Concentration = mass of solute / volume of solvent ## Footnote This formula is essential for determining the concentration of solutions.