# Chapter 9 - Solutions - Additional Questions and Problems - Page 366: 9.113

The molarity of this solution is equal to 0.500 M $NaOH$

#### Work Step by Step

- Calculate or find the molar mass for $NaOH$: $NaOH$ : ( 22.99 $\times$ 1 )+ ( 1.008 $\times$ 1 )+ ( 16.00 $\times$ 1 )= 40.00 g/mol - Using the molar mass as a conversion factor, find the amount in moles: $$8.0 \space g \times \frac{1 \space mole}{ 40.00 \space g} = 0.200 \space mole$$ $1 \space L = 1000 \space mL$ $$Volume(L) = 400. \space mL \times \frac{1 \space L}{1000 \space mL} = 0.400 \space L$$ - Write the molarity expression and evaluate it: $$Molarity(M) = \frac{moles \space of \space solute}{liters \space of \space solution}$$ $$= \frac{0.200 \space mole \space NaOH}{ 0.400 \space L \space solution} = 0.500 \space M \space NaOH \space solution$$

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