Calculate the maximum mass of a metal, with equivalent mass of 20 g, that should be used in an equivalent mass determination with a 100-mL eudometer tube for collection. For the purposes of calculation, assume 80 mL of hydrogen gas produced at standard conditions. (Round to 2 sig figs)

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 )

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.