1.02 Amount of substance

Question 1

Define the Avogadro constant.

Answer 1

The number of particles/atoms/ions in one mole of a substance. (6.022x10 to 23)

Question 2

Write the equation that links mass of 1 mol, mass of 1 atom and Avogadro’s constant.

Answer 2

Mass of one mole = mass of one atom x Avogadro constant.

Question 3

Define percentage yield.

Answer 3

•Describes the efficiency of a reaction
•Calculated by taking the mass of product produced / theoretical maximum (calculated by moles) all x100

Question 4

How do you calculate percentage yield ?

Answer 4

(Mass of useful product / theoretical mass of useful product ) x100

Question 5

What can the percentage yield of a practical be used to investigate ?

Answer 5

Efficiency of practical techniques and whether reactions proceed as estimated.

Question 6

Define atom economy.

Answer 6

Mr of useful product over total Mr of reactants (x100)

Question 7

How do you calculate atom economy ?

Answer 7

Mr of atoms of useful product / Mr of atoms of all reactants.

Question 8

What can the atom economy of a reaction be used to investigate ?

Answer 8

Efficiency of using a specific reaction to produce a product.

Question 9

Write the Ideal Gas Equation with units and symbols.

Answer 9

PV = nRT
Pressure (Pa) x volume (m3) = moles x gas constant x temperature (K)
R = 8.31.

Question 10

What are standard conditions ?

Answer 10

25 C / 298K
1atm / 100kPa.

Question 11

What is the conversion for C to K ?

Answer 11

+273.

Question 12

Define empirical formula.

Answer 12

The simplest whole number ratio of atoms in a compound.

Question 13

What is the equation that links mols, concentration and volume ?

Answer 13

Moles = concentration x volume.

Question 14

What is the equation that links moles, mass and Mr ?

Answer 14

Moles = mass / mr.