Question

One brand of laundry bleach is an aqueous solution containing 4.55% sodium hypochlorite (NaOCI) by mass. What is the molarity of this solution? (Assume a density of 1.02 g/mL)A) 0.548B) 0.611C) 0.623D) 0.723

Answer 1

INFORMATION:

We know that:

- One brand of laundry bleach is an aqueous solution containing 4.55% sodium hypochlorite (NaOCI) by mass

- The density is 1.02 g/mL

And we must find the molarity of this solution

STEP BY STEP EXPLANATION:

To find the molarity, we need to use that

$Molarity=\frac{mol\text{ }solute}{L\text{ }solution}$

So, first we must calculate mol of the solute

To find mol of the solute we need to use that the brand is an aqueous solution containing 4.55% sodium hypochlorite (NaOCI).

In this case, sodium hypochlorite is the solute, so we can represent the percentage as

$4.55\%=\frac{4.55g\text{ }NaOCl}{100g\text{ }solution}$

mol of solute:

Now, using the molar mass of sodium hypochlorite we can convert grams to mol

molar mass of sodium hypochlorite: 74.4 g/mol

$4.55g\cdot\frac{1mol}{74.44g}=0.0611mol$

So, mol solute = 0.061 mol

L of solution:

Then, using the density we can convert g to mL and then mL to L

Density: 1.02 g/mL

1 L = 1000mL

$100g\cdot\frac{1mL}{1.02g}\cdot\frac{1L}{1000mL}=0.098L$

so, L solution = 0.098 L

Finally, replacing in the initial formula

$Molarity=\frac{0.0611mol}{0.098L}=0.623\frac{mol}{L}$

ANSWER:

C) 0.623