Paper 1 - Topic 3, Quantitive Chemistry

Question 1

What is the definition for atom economy

Answer 1

The measure of starting materials that end up as useful products

Question 2

What is the definition for avogadro constant

Answer 2

The number of atoms, molecules or ions in a mole of a given substance

Question 3

What is the definition for avogadros law

Answer 3

Equal amounts in moles of gases occupy the same volume under the same conditions of temperature and pressure

Question 4

What is the definition for concentration

Answer 4

The amount of substance in a certain volumes of a solution

Question 5

What is the definition for conservation of mass

Answer 5

The law of conservation of mass states that no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants

Question 6

What is the definition for limiting reactant

Answer 6

The reactant that is completely used up since it limits the amount of products formed

Question 7

What is the definition for mole

Answer 7

The mole is the unit for amount of substance, chemical amounts are measured in moles

Question 8

What is the equation for calculating percentage by mass

Answer 8

mass of a component x 100
total mass of the mixture

Question 9

What is the definition for percentage yield

Answer 9

The percentage ratio of the actual yield of product from a reaction compared with the theoretical yield

Question 10

What is relative formula mass

Answer 10

The sum of the atomic masses of the atoms in the numbers shown in the formula, it is numerically equal to the mass of one mole of a substance in grams

Question 11

What is the definition for theoretical yield

Answer 11

The maximum amount of product that could be produced from the given reactants, assuming a complete reaction takes place

Question 12

What is the definition for thermal decomposition

Answer 12

The reaction that occurs when heat is applied to a compound causing it to break down into its different chemical constituents

Question 13

What is uncertainty

Answer 13

• all measurements have a degree of uncertainty regardless of precision and accuracy
• uncertainty can be due to the limitations of the measuring equipment or due to the skill of the experimenter carrying out the experiments

Question 14

Define relative atomic mass

Answer 14

The average mass of atoms in an element taking into account masses and abundance of its isotopes

Question 15

How can you increase the precision of a result

Answer 15

Measure to more decimal places or use a more sensitive balance/apparatus

Question 16

What is titration

Answer 16

A technique for finding the concentration of a solution by reacting a known volume of this solution with a solution of a known concentration

Question 17

How do you conduct titration

Answer 17

1. Rinse pipette with a solution of unknown concentration, use pipette to measure out the known volume of this solution
2. Add an indicator
3. Rinse the brunette with a solution of a known concentration, discard the liquid, use a brunette to gradually add the solution of a known concentration
4. When indicator changes colour, volume added is recorded
5. Important to get concordant volume results
6. Use suitable equations to find concentration

Question 18

Why is it not always possible to obtain the theoretical amount of product in a chemical reaction

Answer 18

• reaction may not complete because it is reversible
• some of the product could be lost when separated from the reaction mixture
• side reactions may occur, some of the reactants may react in a different way than expected

Question 19

How do you work out the percentage yield

Answer 19

Question 20

What happens if a reaction appears to involve a change in mass

Answer 20

Could be due to a reactant or product being a gas and the gas has been released into the atmosphere

Question 21

If the relative mass of iron is 56 how much does 1 mole weigh

Answer 21

56g

Question 22

What is the equation that links mass, moles and relative mass

Answer 22

Mass = Mr x moles

Question 23

What equation links mass of a solute, volume and concentration

Answer 23

Mass (g) = concentration (g/dm3) x volume (dm3)

Question 24

If there is a smaller volume or larger mass of solute, what is the concentration like

Answer 24

Higher

Question 25

If there is a larger volume or smaller mass what is the concentration like

Answer 25

Lower

Question 26

How do you work out unknown concentrations

Answer 26

Concentration = moles
volume

Question 27

What is the equation that links moles of solution, volume and concentration is known

Answer 27

Moles = concentration (mol/dm3) x volume (dm3)

Question 28

How do you go from cm3 to dm3

Answer 28

Divide by 1000

Question 29

How do you work out the volume of gas at room temperature

Answer 29

Volume of gas (dm3) at room temp= moles x 24

Question 30

What is the volume of 1 mol of any gas at room temp

Answer 30

24 dm3