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# How much mass of urea $(NH_2CONH_2)$ is required in preparing 5 kg of 0.50 molal solution? (M.wt of urea=60g)

$\begin{array}{1 1}(a)\;150g\\(b)\;120g\\(c)\;170g\\(d)\;200g\end{array}$

Answer: $145.63\;g$
Molar Mass of Urea $(NH_2CONH_2) = 2 (1\times14+2\times)+1\times12+1\times16 = 60\;g\;mol^{-1}$
0.5 molar aques solution of urea mass implies that 1000 g of water contains 0.5 mol $= 0.5 \times 60 = 30\;g$ of urea.
$(1000+30)\; g$ of solution contains $30\;g$ of urea $\rightarrow 5\;kg (5000\;g)$ of solution will contain $\large\frac{30 \times 5000}{1000+30}$$= 145.63\;g$
edited Jul 16, 2014