Question

a particular sample of a zinc-aluminum alloy weighs 3.00 g and has mass percentages of 72.5% Zn and 27.5% Aluminum.

a) How many moles of each element is in the alloy sample?

b) How many theoretical moles of H2(g) will be produced by the reaction of HCl (aq) with each metal and what will be the total number of moles produced?

c) How many actual moles of H2(g) will be produced by the reaction of HCl (aq) with each metal and what will be the total number of moles produced?

d) What volume of dry hydrogen gas measured at 735 torr and 24 ⁰C would be produced by the reaction of this ally with HCl (aq)

Answer 1

a)

Zn/Al

mass of Zn = 0.725*3 = 2.175

mol Zn = mass/MW = 2.175/65.38 = 0.03326 mol of Zn

mass of Al = 0.275*3 = 0.825 g

mol Al = mass/MW = 0.825/26.9 = 0.0306 mol of Al

b)

Zn + 2HCl = ZnCl2 + H2

ratio is 1:1 so

0.03326 mol form Zn

2Al + 6HCl = 2AlCl3 + 3H2

ratio is 2:3 so

0.0306 *3/2 = 0.0459 mol of H2 could bne formed

c)

0.03326  +0.0459 = 0.07916 mol of H2

d)

P = 735 torr = 735/760 = 0.96710 atm

T = 24°C = 297 K

PV = nRT

V = nRT/P = 0.07916 *0.082*297 /0.96710 = 1.9936 L