Amount of Substance

Question 1

Avogadro constant equation

Answer 1

number of particles = number of moles x Avogadro constant

Question 2

What is the value of the Avogadro constant?

Answer 2

6.02x10^23

Question 3

Ideal gas equation

Answer 3

pV=nRT

Question 4

Units of each factor in the ideal gas equation

Answer 4

p = pressure in Pa
V = volume in m3
n = moles
R = 8.31JK-1mol-1
T = temperature in K

Question 5

Balance the equation:

C2H6 + O2 –> CO2 + H2O

Answer 5

C2H6 + 3.5O2 –> 2CO2 + 3H2O

Question 6

Steps for writing an ionic equation

Answer 6

1) write out the full balanced equation
2) split any dissolved ionic species up into ions
3) remove ions that appear on both sides

Question 7

Write an ionic equation for the reaction between sodium hydroxide and nitric acid. Show your workings out

Answer 7

HNO3 + NaOH –> NaNO3 + H2O

H+ + NO3- + Na+ + OH- –> Na+ NO3- + H2O

H+ + OH- –> H2O

Question 8

Find the mass of iron(iii) oxide produced when 28.0g of iron is burnt in air

Answer 8

2Fe + 1.5O2 –> Fe2O3

Mr of Fe = 55.8
Moles = mass/Mr
Moles = 28/55.8
Moles = 0.502

Molar ratio = Fe2O3 = 2:1

Question 9

Difference between degrees Celsius and kelvin

Answer 9

+273

Question 10

How to make a standard solution

Answer 10

Workout number of moles of solid needed
Moles = concentration x volume

Workout mass of solid needed
Mass = Mr x moles

Weigh weighing boat on scales

Weigh out mass needed taking into account weight of weighing boat

Empty solid into 250cm3 volumetric flask

Wash bottle the weighing boat to ensure all solid is in the flask

Top flask up with distilled water to the 250cm3 line

Ensure meniscus of water is on the line

Bung the flask

Invert flask to mix contents

Workout concentration of standard solution
Moles = (concentration x volume)/1000
Equal the moles up based on molar ratio
Concentration = (moles x 1000)/volume

Question 11

How to carry out a titration

Answer 11

Wash pipette out with alkali
Pipette alkali into conical flask
Add a few drops of phenolphthalein into conical flask
Wash burette out with acid of known concentration
Add acid to conical flask until goes pink to colourless
Record volume of acid used
Workout moles of acid (moles = concentrations x volume)
Workout moles of alkali from molar ratio
Workout concentration of alkali (concentration = moles/volume)

Question 12

What is atom economy?

Answer 12

Amount of wanted atoms produced

Question 13

Advantages of high atom economy

Answer 13

Efficient
Less waste
Sustainable

Question 14

Atom economy equation

Answer 14

% atom economy = (molecular mass of desired product x sum of molecular masses of all reactants) x 100

Question 15

Theoretical yield equation

Answer 15

% yield = (actual yield/theoretical yield) x 100