We can use stoichiometry to determine the volume of hydrogen chloride gas produced.

The balanced chemical equation for the reaction between chlorine and hydrogen is:

Cl2(g) + H2(g) → 2HCl(g)

From the equation, we can see that 1 mole of chlorine gas reacts with 1 mole of hydrogen gas to produce 2 moles of hydrogen chloride gas.

We are given that 40 cm3 of chlorine gas is used. We can convert this to moles using the ideal gas law:

PV = nRT

where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature.

Assuming standard temperature and pressure (STP), we have:

P = 1 atm

V = 40 cm3 = 0.040 L

R = 0.08206 L atm/mol K

T = 273 K

Substituting these values into the equation, we get:

n = PV/RT = (1 atm)(0.040 L)/(0.08206 L atm/mol K)(273 K) = 0.0017 mol

Since 1 mole of chlorine gas produces 2 moles of hydrogen chloride gas, 0.0017 mol of chlorine gas will produce 0.0034 mol of hydrogen chloride gas.

We can then convert this back to volume using the ideal gas law:

V = nRT/P = (0.0034 mol)(0.08206 L atm/mol K)(273 K)/(1 atm) = 0.079 L

Therefore, the volume of hydrogen chloride gas produced is 0.079 L or 79 cm3.