Question

7. Look at the equipment you are using in this experiment. Consider an experiment where 0.129 g sample of your sample of Al-Zn alloy is reacted with dilute HCl(aq) to displace 147 g of water from the 500 mL and collected into the 400 mL beaker. One the day of the experiment the barmetric pressure is 982 mbar and the water temperature is 23 deg C.

a) V olume of displace water

b) Pressure of dry hydrogen,

c) Moles of hydrogen

d) Find the number of moles/g, NH2

___________ L

___________ atm

___________ mole

___________ mole/g

Answer 1

Given data:

The mass of a sample of Al-Zn alloy = 0.129 g

The mass of displaced water = 147 g

The density of water = 1 g/mL

Therefore, the volume of displaced water = 147 mL, i.e. 147*10^-3 L = 1.47*10^-1 L

The reaction of Zn with HCl: Zn + 2HCl ZnCl₂ + H₂

The reaction of Al with HCl: 2Al + 6HCl 2AlCl₃ + 3H₂

n(H₂) = {n(Al)*3 mol H₂ / 2 mol Al} + {n(Zn)*1 mol H₂ / 1 mol Zn}

P(wet H₂) = V (H₂) / {n(H₂)*R*T} (From ideal gas equation)

P(dry gas) = P(wet gas) - P(H₂O), i.e. P(dry H₂) = P(wet H₂) - aqueous tension

n(H₂) = 1 mol / 2 g (Note: The molar mass of H₂ = 2 g mol^-1)