Question

a)A chemist requires 0.732 mol Na2CO3 for a reaction. How many grams does this correspond to?

b)The reaction between iron(II) oxide and carbon monoxide produces iron and carbon dioxide. How many moles of iron can be obtained when 4.25 mol FeO reacts with an excess of CO?

c)The reaction between hydrochloric acid and aluminum produces hydrogen gas and aluminum chloride. The balanced reaction equation is given below. How many moles of H2 can be obtained when 4.20 mol HCl reacts with an excess of Al?

d)In the following reaction, how many grams of calcium hydroxide, Ca(OH)2, will be needed to react with 31.9 g of hydrochloric acid, HCl?

Answer 1

a)

moles of Na2CO3 = 0.732 mol

molar mass of Na2CO3 = 106 g/mol

moles = mass / molar mass

0.732 = mass / 106

mass of Na2CO3 = 77.6 g

b)

FeO (s) +   CO (g)   ----------------> Fe (s) + CO2 (g)

1 mol FeO   ----------------> 1 mol Fe

4.25 mol FeO -------------> 4.25 mol Fe

moles of iron obtained = 4.25 mol

c)

6 HCl   + 2 Al    ---------------> 3 H2 + 2 AlCl3

6 mol HCl   -----------> 3 mol H2

4.20 mol HCl   ------------> ??

moles of H2 formed = 4.20 x 3 / 6 = 2.10

moles of H2 formed = 2.10