Question

A piece of zinc reacts with hydrochloric acid to form zinc chloride and hydrogen gas, which is collected over water at 150 C into a large flask. The total pressure is adjusted to 1.00 bar, and the volume is 1495 mL

(a) What is the PH2? (ANSWER = 0.98 bar)

(b) What is the mass of H2? (ANSWER = 0.12 g)

(c) What mass of Zn was used in this process? (ANSWER = 4.0 g

please show me the steps>>>>

Answer 1

(a) What is the PH2? (ANSWER = 0.98 bar)

The vapor pressure of water is 22.38 torr= 0.03117 bar

The reaction of Zn and HCl is as follows:

Zn + 2HCl = ZnCl2 + H2

   The vapor pressure of H2 = total pressure - pressure of water

= 1.00 bar-0.03117 bar

= 0.968 bar

(b) What is the mass of H2? (ANSWER = 0.12 g)

0.968 bar = 0.955 atm

Here volume = 1465 ml = 1.495 L

Tem = 150 c= 423 K

Now calculate the number of moles of H2

PV = n RT

n = PV/RT

n = 0.955 *1.495/0.08206*423

= 0.041 moles

Amount of H2= Number of moles * molar mass

= 0.041 moles* 2.016 g/ moles

=0.083 g

(c) What mass of Zn was used in this process? (ANSWER = 4.0 g

The reaction of Zn and HCl is as follows:

Zn + 2HCl = ZnCl2 + H2

Moles of H2 = 0.041 moles

0.041 moles * 1 mole Zn / 1 mole H2

= 0.041 moles Zn

Amount of Zn= 0.041 moles *65.38 g/ moles

= 2.68 g