Everything Science Grade 10

CHAPTER 19. QUANTITATIVE ASPECTS OF CHEMICAL CHANGE 19.4

% yield=theoretical yieldactual yield ×100 = 22 ,, 3242 ×100 = 94,64%

Example 18: Calculating the mass of reactants and prod-

ucts

QUESTION

Barium chloride and sulphuric acid react according to the following equation to

produce barium sulphate and hydrochloric acid.

BaCl 2 +H 2 SO 4 →BaSO 4 + 2HCl

If you have 2 g of BaCl 2 :

1. What quantity (in g) of H 2 SO 4 will you need for the reaction so that all the

barium chloride is used up?

2. What mass of HCl is produced during the reaction?

SOLUTION

Step 1:Find the number of moles of barium chloride

n=mM=^2 g

208 , 2 g·mol−^1

= 0, 0096 mol

Step 2:Find the number of moles of sulphuric acid

According to the balanced equation, 1 mole of BaCl 2 will react with

1 mole of H 2 SO 4. Therefore, if 0 , 0096 mol of BaCl 2 react, then there

must be the same number of moles of H 2 SO 4 that react because their

mole ratio is1 : 1.

Step 3:Find the mass of sulphuric acid

m=n×M= 0, 0096 mol× 98 , 12 g·mol−^1 = 0, 94 g

(answer to 1)

Step 4:Find the moles of hydrochloric acid

According to the balanced equation, 2 moles of HCl are produced for

every 1 mole of the two reactants. Therefore the number of moles of

Chemistry: Chemical change 357