2.Amounts of Substance

Question 1

Define relative atomic mass

Answer 1

Average mass of an atom relative to 1/12th mass of a carbon-12 atom

Question 2

Define relative molecular mass

Answer 2

Average mass of a molecule relative to 1/12th mass of a carbon-12 atom

Question 3

What is relative formula mass used for

Answer 3

To describe Mr for ionic compounds as they don’t exist as molecules

Question 4

What is Avogadro’s constant

Answer 4

6.022 x 10^23

Question 5

Define Avogadro’s constant

Answer 5

Is the number if atoms in 12g of carbon-12 or a mole

Question 6

What is the ideal gas equation

Answer 6

PV=nRT

Question 7

What are the units for the ideal gas equation

Answer 7

• pressure Pa
• volume m^3
• moles mol
• gas constant JK^-1 mol^-1
• temperature K

Question 8

What is K at 0 C

Answer 8

273

Question 9

Define empirical formula

Answer 9

Empirical formula is the simplest whole number ratio of

atoms of each element in a compound

Question 10

Define molecular formula

Answer 10

Molecular formula is the actual number of atoms of each element in a compound.

Question 11

How do you write an ionic equation

Answer 11

• write normal equation
• split into ions present
• cancel out ions that appear on each side (spectator ions)

Question 12

What is the equation for % atom economy

Answer 12

(mass of desired product / total mass of reactants) x 100

Question 13

What is the equation for % yield

Answer 13

Number of moles (or grams) of a specified product/ theoretical maximum number of moles (or grams) of the product x 100

Question 14

What is a mole

Answer 14

An amount of substance that contains 6.022 x 10^23 particles

Question 15

How do you convert cm^3 to m^3

Answer 15

Divide by 100^3

Question 16

How to find the number of units of the empirical formula in the molecular formula

Answer 16

divide the relative molecular mass by the relative mass of the empirical formula