C3

Question 1

What is the law of the conservation of mass?

Answer 1

Mass is neither gained or lost during a chemical reaction. Mass of reactants= mass of products

Question 2

What is relative atomic mass?

Answer 2

The RAM is the average mass of atoms in an element- takes into account the masses of its isotopes (e.g. Cl= RAM of 35.5)

Question 3

What is the relative formula mass?

Answer 3

The sum of all the RAM’s in the formula

Question 4

What is Avogadro’s number?

Answer 4

6.02 x 10 to the power of 23

Question 5

What is Avogadro’s constant?

Answer 5

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

Question 6

What is the equation that links mass, molecules and molecular mass together?

Answer 6

Mass= Mr x Moles

Question 7

What does a limiting reactant in a chemical reaction mean?

Answer 7

In a chemical reaction that involves two reactants, it’s common to have too much of one reactant to ensure all of the other reactant is used up. The reaction that’s completely used up is the limiting reactant.

Question 8

What is the formula that links concentration, mass and volume together, and what are their units?

Answer 8

Concentration (grams per dm3) - Mass (g) / volume (dm3)
Concentration (mol per dm3) - Moles/ volume (dm3)

Question 9

What is the molar volume of a gas at room temperature and pressure?

Answer 9

24dm3 for 1 mole of gas at room temp and pressure

Question 10

What is titration?

Answer 10

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

Question 11

What is the RPA for titration?

Answer 11

1. Use a pipette to measure out the known volume of this solution
2. Add an indicator
3. Use a buret with a solution of the known concentration. Fill it up and slowly add the solution of the known concentration
4. Swirl the conical flask (where the known volume is held) as you add the known concentration
5. When the indicator changes colour (should turn pink), measure the volume
6. Repeat- make sure the volumes are consistent

Question 12

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

Answer 12

1. The reaction may be reversible
2. Some product may have been lost when it is separated from the reaction mixture
3. Reactants may not be pure

Question 13

How to calculate the percentage yield in a product in a chemical reaction?

Answer 13

% yield = (actual mass of a product / theoretical mass) x 100

Question 14

What is atom economy?

Answer 14

A measure of the amount of starting materials that end up as useful products
Ratio of RFM of desired product to RFM of reactants