What mass of h2 gas (in
g. would be produced by the complete reaction of the aluminum block?

First lets calculate the moles of aluminum (molar mass is 27 gram/mol):

n = m/M = 14.9 / 27 = 0.551 mole of Al

According to the reaction between sulfuric acid and aluminum:

From 2 moles of aluminum ==> we get 3 moles of Hydrogen gas

so, let's do cross multiplication

0.551 ==> 0.551 * 3/2 = 0.83 mole of H2

So, from this reaction we got 0.83 mole of H2 gas

knowing that the molar mass of H2 is 2 gram/mol, the mass of the gas is.

m = n * M = 0.83 * 2 = 1.66 gram of H2

1. they vary with a higher number because boiling is way hotter than melting