C4 - Chemical Calculations

Question 1

How do you work out the relative atomic mass of a chemical?

Answer 1

Add together each element’s amount of protons and neutrons, then add all the results together.

Question 2

What is a mole?

Answer 2

6.02x10^23

Question 3

How do you calculate moles from masses?

Answer 3

Number of Moles = Mass (g) / Relative Atomic Mass

Question 4

How do you calculate masses from moles?

Answer 4

Mass (g) = Number of Moles x Relative Atomic Mass

Question 5

What is percentage yield?

Answer 5

The mass of product produced compared to the maximum that could have been produced, calculated using Yield = Mass Produced (g) / Maximum Mass Possible (g) x 100.

Question 6

What is atom economy?

Answer 6

The amount of material used that turns into useful material in a reaction, calculated using Atom Economy = Relative Mass of Useful Product / Relative Mass of Reactants * 100

Question 7

What is concentration?

Answer 7

The amount of solute compared to the total volume of a solution, calculated with Concentration = Amount of Solute (g) / Volume of Solution (dm^3)

Question 8

What is titration?

Answer 8

The method used to accurately measure what volumes of acid and alkali react together completely. The method is as follows:

• Mix in some indicator with a known amount of alkali.
• Slowly drip in acid through a burette until the indicator changes colour.
• Record the volume of acid used to reach that point.

Question 9

How do you work out how many moles of gas are in a volume?

Answer 9

Moles of Gas = Volume of Gas (dm^3)/ 24dm^3