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Model Paper 1 — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistryModel Paper 13 Marks
Question
A sugar syrup of weight 214.2 g contains 34.2 g of sugar $\left( C _{12} H _{22} O _{11}\right)$. Calculate
i. molal concentration, and
ii. mole fraction of sugar in the syrup
✓

Answer


$\begin{aligned} & \text { i. } \text { Weight of sugar syrup }=214.2 g \\ & \text { Weight of sugar in syrup }=34.2 g \\ & \text { weight of water in syrup }=214.2-34.2=180.0 g \\ & \text { Moles of sugar }=\frac{34.2}{342}=0.1(\text { Molar mass }=342) \\ & \text { Molality }=\frac{0.1}{180} \times 1000=0.56 m \\ & \text { ii. } \text { Moles of sugar }=\frac{34.2}{342}=0.1 \\ & \text { Moles of water }=\frac{180}{18}=10 \\ & \text { Mole fraction of sugar }=\frac{0.1}{10+0.1} \\ & =0.0099\end{aligned}$

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