Question

Calculate the number of moles of H2 produced in the reaction of Mg(s) with HCl(aq). Mg(s) is the

Answer 1

Explanation:

Moles of metal,

=

4.86

⋅

g

24.305

⋅

g

⋅

m

o

l

−

1

=

0.200

m

o

l

.

Moles of

H

C

l

=

100

⋅

c

m

−

3

×

2.00

⋅

m

o

l

⋅

d

m

−

3

=

0.200

m

o

l

Clearly, the acid is in deficiency ; i.e. it is the limiting reagent, because the equation above specifies that that 2 equiv of HCl are required for each equiv of metal.

So if

0.200

m

o

l

acid react, then (by the stoichiometry), 1/2 this quantity, i.e.

0.100

m

o

l

of dihydrogen will evolve.

So,

0.100

m

o

l

dihydrogen are evolved; this has a mass of

0.100

⋅

m

o

l

×

2.00

⋅

g

⋅

m

o

l

−

1

=

?

?

g

.

If 1 mol dihydrogen gas occupies

24.5

d

m

3

at room temperature and pressure, what will be the VOLUME of gas evolved?