1. Calculations: examples and strategy
Intermediate 2 Chemistry

2. Unit 1 calculations Rate from time / time from rate
Rate from change of quantity
Moles from mass / mass from moles
Mass of product from mass of reactant

3. Calculating rate of reaction from time OR Calculating time from rate of reaction

5. Strategy Use time = 1/rate (ignore the temperature, it’s not required)
Write numerical answer with correct units

6. Answer

8. Strategy
Use time = 1/rate
Write numerical answer with correct units

9. Answer

10. Calculating rate of reaction from change in quantity of reactant

12. Strategy Use rate = change/time
Write numerical answer with correct units

15. Strategy Use rate = change/time Calculate the change from the graph
Write numerical answer with correct units

16. Answer

17. Calculating moles of a substance from the mass of that substance

19. Strategy
Using page 4 of the data book, calculate the formula mass of the substance
Set out working in the form:
… g → … mol
3. Use proportion to calculate the mass, first calculating the number of moles in 1g, then the number of moles in the mass given in the question

21. Calculating mass of product from mass of reactant

23. Strategy
Write a moles ratio for the two substances you are interested in
Using page 4 of the data book, calculate the formula mass of each substance
Multiply the formula mass of each substance by the appropriate number of moles (from the moles ratio)
Use proportion to calculate the mass required for the information given in the question

24. Answer

26. Strategy
Write a moles ratio for the two substances you are interested in
Using page 4 of the data book, calculate the formula mass of each substance
Multiply the formula mass of each substance by the appropriate number of moles (from the moles ratio)
Use proportion to calculate the mass required for the information given in the question

27. Answer

29. Strategy
Write a moles ratio for the two substances you are interested in
Using page 4 of the data book, calculate the formula mass of each substance
Multiply the formula mass of each substance by the appropriate number of moles (from the moles ratio)
Use proportion to calculate the mass required for the information given in the question

30. Answer

32. Strategy
Write a moles ratio for the two substances you are interested in
Using page 4 of the data book, calculate the formula mass of each substance
Multiply the formula mass of each substance by the appropriate number of moles (from the moles ratio)
Use proportion to calculate the mass required for the information given in the question

33. Answer

34. Unit 3 calculations Moles from concentration and volume
Mass from concentration and volume
Titrations (concentration of an unknown reactant from a known concentration/volume of a known reactant

35. Calculating number of moles from a concentration and volume of solution

37. Strategy Use the formula n = cv
Turn any volumes into litres e.g. 200cm3 is 0.2l
Calculate the number of moles (n) for each

40. Strategy Use the formula n = cv
Turn any volumes into litres e.g. 200cm3 is 0.2l
Calculate the number of moles (n) for each

41. Answer

43. Answer

44. Calculating mass from a concentration and volume of solution

46. Strategy Use n = cv to calculate number of moles
Use the formula and the data book to calculate the mass of one mole
Use proportion to calculate the mass of however many moles you actually have (worked out in 1)

47. Titration calculations (calculating the concentration of an acid or alkali from the concentration and volume of an acid or alkali it is reacted with)

49. Strategy
Use the formula n = cv to calculate the number of moles of the substance you know the concentration and volume of (make sure volume is in litres)
Use the moles ratio from the balanced equation to calculate the number of moles of the other substance
Use the formula c = n/v to calculate the concentration of the other substance (make sure volume is in litres)
Include the correct units: mol l-1

50. Answer