If you produce 35.7 grams of sodium chloride how many molecules of Chlorine gas were needed?
2Na + Cl2 --> 2NaCl
(PLS HELP)

number of molecules of chlorine gas are needed.

Explanation:

The number of moles is defined as the ratio of the mass of a substance to its molar mass. The equation used is:

......(1)

Given mass of sodium chloride = 35.7 g

Molar mass of sodium chloride = 58.44 g/mol

Plugging values in equation 1:

The given chemical equation follows:

By the stoichiometry of the reaction:

If 1 mole of sodium chloride is produced from 2 moles of chlorine gas

So, 0.611 moles of sodium chloride will be produced from = of chlorine gas

According to the mole concept:

1 mole of a compound contains number of molecules

So, 1.222 moles of chlorine gas will contain = number of molecules

Hence, number of molecules of chlorine gas is needed.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.