Question

a .535 gram sample of metal M reacts completely with sulfuric acid according to :

M(s) +H2SO4----> MSO4(aq) + H2 (g)

a volume of 247 ml of hydrogen is collected over water; the water level in the collecting vessel is the same as the outside level. atmospheric pressure is 756.0 Torr and the temprature is 25C . Calculate the molar mass of the metal

____g/mol

Answer 1

Answer:-

The vapour pressure of the water in the collecting vessel is 23.8 torr

Since the total pressure is the atmospheric pressure

The pressure due to the hydrogen is,

756.0 - 23.8 = 732.2 torr

SInce you are given volume, pressure, and temperature, you can use the ideal gas law

PV = nRT

Where,

P = the pressure

V = the volume

n = the number of moles

R = the universal gas constant

T = the temperature

to solve for n, the number of moles of gas.

The universal gas constant, R, is usually given as

R=0.082atm⋅L / mol⋅K

Which means that you will have to convert the pressure of the gas from torr to atm by using the conversion factor

1 atm = 760 torr

So, plug in your values and solve for n

n = PV / RT

n = ((732.2/760) × 0.247) / (( 0.082atm⋅L / mol⋅K)(273 + 25)

n = 0.00974 mole of H2

This means that the molar mass of the gas will be equal to

Mm = m / n

Where,

Mm = the molar mass

m = given mass

n = the number of moles

Mm = 0.535g / 0.00974 mole

Mm = 54.938 g/mole

This is the molar mass of Manganese