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Chemistry Question on Mole concept and Molar Masses

The molality of solution containing 15.20 g15.20\, g of urea, (molar mass = 6060) dissolved in 150 g150 \,g of water is

A

1.689 mol kg−11.689 \, mol \, kg^{-1}

B

0.1689 mol kg−10.1689 \, mol \, kg^{-1}

C

0.5922 mol kg−10.5922 \, mol \, kg^{-1}

D

0.2533 mol kg−10.2533 \, mol \, kg^{-1}

Answer

1.689 mol kg−11.689 \, mol \, kg^{-1}

Explanation

Solution

molality = mass of urea  molar mass of urea × mass of water in kg=\frac{\text { mass of urea }}{\text { molar mass of urea } \times \text { mass of water in } kg }
molality =15.20 g60 g/mol×0.150 kg=\frac{15.20\, g }{60\, g / mol \times 0.150\, kg }
molality =1.689 mol/kg=1.689\, mol / kg