Question

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: 2NaCl + 2H2O → 2NaOH + Cl2 + H2. How many grams of chlorine gas, Cl2, are given off if 7.5 grams of sodium chloride, NaCl, are decomposed? The molecular mass of NaCl is 58.44 g/mole. The molecular mass of Cl2 is 70.90 g/mole.

Answer 1

m(NaCl)/{2M(NaCl)}=m(Cl₂)/M(Cl₂)

m(Cl₂)=M(Cl₂)m(NaCl)/{2M(NaCl)}

m(Cl₂)=70.90*7.5/{2*58.44}=4.55 g

m(Cl₂)=4.55 g

Answer 2

Answer : The mass of chlorine gas given off are 4.54 grams.

Solution : Given,

Mass of
`NaCl` = 7.5 g

Molar mass of
`NaCl` = 58.44 g/mole

Molar mass of
`Cl_2` = 70.90 g/mole

First we have to calculate the moles of
`NaCl`.

`\text{ Moles of }NaCl=\frac{\text{ Mass of }NaCl}{\text{ Molar mass of }NaCl}=(7.5g)/(58.44g/mole)=0.128moles`

Now we have to calculate the moles of
`Cl_2`

The balanced chemical reaction is,

`2NaCl+2H_2O\rightarrow 2NaOH+Cl_2+H_2`

From the balanced reaction we conclude that

As, 2 mole of
`NaCl` react to give 1 mole of
`Cl_2`

So, 0.128 mole of
`NaCl` react to give
`(0.128)/(2)=0.064` mole of
`Cl_2`

Now we have to calculate the mass of
`Cl_2`

`\text{ Mass of }Cl_2=\text{ Moles of }Cl_2* \text{ Molar mass of }Cl_2`

`\text{ Mass of }Cl_2=(0.064moles)* (70.90g/mole)=4.54g`

Therefore, the mass of chlorine gas given off are 4.54 grams.