Q. 15 - An Introduction to General, Organic, and Biological Chemistry

Question

Bleach is often added to a wash to remove stains from clothes, The active ingredient in bleach is sodium hypochlorite (NaClO). A bleach solution can be prepared by bubbling chlorine gas into a solution of sodium hydroxide to produce liquid water and an aqueous solution of sodium hypochlorite and sodium chloride. A typical bottle of bleach has a volume of$1.42\mathrm{gal}$, with a density of$1.08 \mathrm{g}/\mathrm{mL}$ and contains $282 \mathrm{g}$ of $\mathrm{NaClO},(6.2,6.3,7.4,7.8,8.6,9.4)$

a. Is sodium hypochlorite an ionic or a molecular compound?

b. What is the mass/volume percent $(\mathrm{m}/\mathrm{v})$of sodium hypochlorite in the bleach solution?

c. Write a balanced chemical equation for the preparation of a bleach solution.

d. How many liters of chlorine gas at STP are required to produce one bottle of bleach?

Step-by-Step Solution

Answer

(Part a)

Sodium hypochlorite has an ionic bond between ${\mathrm{Na}}^{+}$and ${\mathrm{ClO}}^{*}$ ions. For this reason, this is an ionic compound

(Part b)

Therefore, the mass/volume percent (m/v) of sodium hypochlorite in the bleach solution is $5.25\%$ (m/v)

(Part c)

The balanced chemical equation of the reaction is as follows:

${\mathrm{Cl}}_2( \mathrm{g})+2\mathrm{NaOH}\left(\mathrm{aq}\right)⟶\mathrm{NaCl}\left(\mathrm{aq}\right)+\mathrm{NaClO}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

(Part d)

Therefore,$84.9 \mathrm{L}$ of chlorine gas at STP are required to produce one bottle of bleach.

Step 1 : Given information (Part a)

That  are given sentences are : 

Calculate the mass of sodium hypochlorite$\left(\mathrm{NaClO}\right)$

Step 2: Explanation

Given volume of bleach solution is$1.42\mathrm{gal}$

Convert gal to$\mathrm{mL}$ is as follows:

$$\begin{gathered} =1.42\mathrm{gal}\times \frac{3785.41 \mathrm{mL}}{1\mathrm{gal}} \\ =5375.3 \mathrm{mL} \end{gathered}$$

Density of bleach solution $=1.08 \mathrm{g}/\mathrm{mL}$

Calculate the mass of sodium hypochlorite$\left(\mathrm{NaClO}\right)$ in the bleach solution is $282 \mathrm{g}$.

Step 3: Given information (Part a)

That are given sentences are : (Part a)

Sodium hypochlorite

Step 4: Explanation (Part a)

(a)

Sodium hypochiorite has an ionic bond between ${\mathrm{Na}}^{+}$and $\mathrm{ClO}°$ ions. For this reason, this is an ionic compound

Step 5: Given information (Part b)

That are given equations are : (b)

Calculate the mass by volume percent by using the following expression.

Step 6: Explanation (Part b)

Calculate the mass by volume percent by using the following expression.

$$\begin{gathered} \text{ Mass percent }(\mathrm{m}/\mathrm{v})=\frac{\text{ Solute mass }}{\text{ Solution volume }}\times 100\% \\ =\frac{282 \mathrm{g}}{5375.3 \mathrm{mL}}\times 100\% \\ =5.25\% \end{gathered}$$

Therefore, the mass/volume percent (m/v) of sodium hypochlorite in the bleach solution is$5.25\%$$(\mathrm{m}/\mathrm{v})$

Step 7: Given information (Part c)

That are given equations are : (c)

A bleach solution is prepared by bubbling chlorine gas

Step 8: Explanation (Part c)

(c)

A bleach solution is prepared by bubbling chlorine gas into a solution of sodium hydroxide to produce liquid water and an aqueous solution of sodium hypochlorite and sodium chloride. The balanced chemical equation of the reaction is as follows:

${\mathrm{Cl}}_2( \mathrm{g})+2\mathrm{NaOH}\left(\mathrm{aq}\right)⟶\mathrm{NaCl}\left(\mathrm{aq}\right)+\mathrm{NaClO}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{I}\right)$

Step 9: Given information (Part d)

That are given equations are : (d)

Calculate the moles of sodium hypochlorite in the bleach solution are as follows:

Step 10: Explanation (d)

The balanced reaction is,

${\mathrm{Cl}}_2( \mathrm{g})+2\mathrm{NaOH}\left(\mathrm{aq}\right)⟶\mathrm{NaCl}\left(\mathrm{aq}\right)+\mathrm{NaClO}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Mass of sodium hypochiorite in the bleach solution is$282 \mathrm{g}$.

Calculate the moles of sodium hypochlorite in the bleach solution are as follows:

$$\begin{gathered} \text{ Moles }=\frac{\text{ mass of }\mathrm{NaClO}}{\text{ Molar mass of }\mathrm{NaClO}} \\ =\frac{282 \mathrm{g}}{74.44 \mathrm{g}/\mathrm{mol}} \\ =3.79 \end{gathered}$$

According to the balance chemical equation,

Mole ratio of ${\mathrm{Cl}}_2$ and $\mathrm{NaClO}$ are in$1:1$ ratio.

Step 11: Given information

That are given sentences are :

Therefore, volume occupied by $3.79$moles of Cl2 gas at STP is,

Step 12: Explanation

So, moles of chlorine gas required are$3.79$
 moles.

At STP, volume occupied by 1 mole of $\mathrm{Cl}2$ gas is $22.4 \mathrm{L}$

Therefore, volume occupied by$3.79$moles of Cl2 gas at STP is,

$$\begin{gathered} =3.79 \mathrm{mol}\times \frac{22.4 \mathrm{L}}{1 \mathrm{mol}} \\ =84.9 \mathrm{L} \end{gathered}$$

Therefore,$84.9 \mathrm{L}$ of chlorine gas at STP are required to produce one bottle of bleach.