Chapter 13 - Solutions and Their Physical Properties - 13-1 Concept Assessment - Page 559: 13-1

$3.01 \times 10^{23} $ water molecules

$$0.5 = \frac{amount \space of \space water}{1 \space mole}$$ $$amount \space of \space water = 0.5 \times 1 \space mole = 0.5 \space mole$$ $$0.5 \space mole \times \frac{6.02 \times 10^{23} \space molecules}{1 \space mole} = 3.01 \times 10^{23} \space molecules$$