How many kilograms of chlorine gas is needed to produce 45.0 grams of hydrochloric acid?

43.76 g = 0.04376 Kg

Explanation:

The equation of the reaction is given as;

H2 + Cl2 --> 2HCl

From the equation;

1 mol of Cl2 produces 2 mol of HCl

Converting to mass;

Mass = Number of mol * Molar mass

Cl2;

Mass = 1 mol * 70.906 g/mol = 70.906 g

HCl;

Mass = 2 mol * 36.458 g/mol = 72.916 g

This means;

70.906 g of Cl2 produces 72.916 g of HCl

x g of Cl2 would produce 45g of HCl

70.906 = 72.916

x = 45

x = 45 * 70.906 / 72.916

x = 43.76g