Answer:
Step-by-step explanation:
In the equivalent mass measurement , one gram equivalent of metal produces 11200 mL of hydrogen gas .
11200 mL hydrogen gas is produced by 1 gram equivalent of gas at STP
11200 mL hydrogen gas is produced by 20 g of gas at STP
80 mL hydrogen gas is produced by 20 x 80 / 11200 g of gas at STP
= 142.85 mg .
= 140 mg . ( rounded to 2 sig figures )