one brand of laundry bleach is an aqueous solution containing 4.55% sodium hypochlorite (naocl) by mass…

Explanation:

Step1: Assume 1 L of solution

The density of the solution is $1.02\ g/mL$. For a $V = 1\ L=1000\ mL$ solution, the mass of the solution $m_{solution}$ is calculated by the density - mass formula $m=\rho V$. So $m_{solution}=\rho V=1.02\ g/mL\times1000\ mL = 1020\ g$.

Step2: Calculate the mass of NaOCl

The solution is $4.55%$ sodium hypochlorite by mass. So the mass of $NaOCl$, $m_{NaOCl}=m_{solution}\times4.55%=1020\ g\times0.0455 = 46.41\ g$.

Step3: Calculate the molar mass of NaOCl

The molar mass of $NaOCl$: $M_{NaOCl}=22.99\ g/mol + 16.00\ g/mol+35.45\ g/mol=74.44\ g/mol$.

Step4: Calculate the number of moles of NaOCl

The number of moles of $NaOCl$, $n=\frac{m}{M}$. So $n_{NaOCl}=\frac{m_{NaOCl}}{M_{NaOCl}}=\frac{46.41\ g}{74.44\ g/mol}\approx0.623\ mol$.

Step5: Calculate the molarity

Molarity $M=\frac{n}{V}$. Since $V = 1\ L$ and $n = 0.623\ mol$, the molarity of the solution $M = 0.623\ M$.

Answer:

C. 0.623 M