Chemistry question pls help

Question

A 0.623 g sample of a metal, M, reacts completely with sulfuric acid according to M(s)+H2SO4(aq)⟶MSO4(aq)+H2(g) A volume of 283 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 temperature is 25 °C. The vapor pressure of water at 25 °C is 23.8 Torr. Calculate the molar mass of the metal.

Answer 1

Bella,

You would use the ideal gas equation to find the number of moles of gas, which can help you calculate the molar mass.

Ideal Gaw Law---------------> PV = nRT

We can list the variables that we currently have.

V = 283 mL (convert to L by dividing by 1000 ....... 0.283 L)

T = 25 °C (convert to K by adding 273 ....... 298 K)

We can calculate the pressure of the gas by subtracting the pressure of water vapor from the total pressure. Since the gas was collected over water, some of that total gas pressure will be the pressure from water vapor.

P of gas = 756. 0 Torr - 23.8 Torr = 732.2 Torr (convert to atm by dividing by 760 ........ 0.963 atm)

R is the ideal gas constant which has a value of 0.08206 L.atm/mol.K

When we rearrange the equation, we get n = PV/RT, so when we plug our values in, we can find n (the number of moles)

n = 0.963 atm × 0.283 L/ 0.08206 L.atm/mol.K × 298 K

n = 0.0111 moles of H₂

From the balanced equation, there's a 1:1 mole ratio of H₂ to the metal, M, so the ni. of moles of M also - 0.0111 moles.

Molar mass = g/mol so 0.623g/0.0111 moles = 56.1 g/mol