Use the problem below to answer the question: When a current is passed through a solution of salt water, sodium chloride decomposes according to the following reaction: NaCl + H2O → NaOH + Cl2 + H2 How many grams of chlorine gas, Cl2 are given off if 7.5 grams of sodium chloride, NaCl, are decomposed? Is this equation balanced?
Answer: 4.544 grams of chlorine gas is produced in the given reaction.
Explanation: Number of moles can be calculated by using the formula:
\(Moles=\frac{\text{given mass}}{\text{Molar mass}}\) ... (1)
Molar mass of NaCl = 58.5 g/mol
Given mass of NaCl = 7.5 grams
Moles of NaCl is calculated by:
\(Moles=\frac{7.5g}{58.5g/mol}\)
Moles of NaCl = 0.128 moles
The given equation is not balanced. For any further calculation, we first need to balance the equation.
The balanced chemical equation follows:
\(2NaCl+2H_2O\rightarrow 2NaOH+Cl_2+H_2\)
By Stoichiometry,
2 moles of NaCl produce 1 mole of chlorine gas
So, 0.128 moles of NaCl will produce = \(\frac{1}{2}\times 0.128\) = 0.064 moles of chlorine gas
Mass of Chlorine gas is calculated by using equation 1, we get
Molar mass of \(Cl_2\) = 71 g/mol
Putting the values in above equation, we get
\(0.064mol=\frac{\text{Given mass}}{71g/mol}\)
Mass of \(Cl_2\) produced = 4.544 grams