SATHEE: Solutions Question 257

Solutions Question 257

Question: The cryoscopic constant for acetic acid is 3.6 K kg/mol. A solution of 1 g of a hydrocarbon in 100 g of acetic acid freezes at $16.14^{\circ} C$ instead of the usual $16.60^{\circ} C$ . The hydrocarbon contains 92.3% carbon. What is the’molecular formula-

Options:

A) $C_{6} H_{6}$

B) $C_{6} H_{12}$

C) $C_{8} H_{18}$

D) $C_{10} H_{6}$

Show Answer

Answer:

Correct Answer: A

Solution:

$K_{b} = 3.6 K, k g / m o l .$

$Δ T_{f} = 16.6 - 16.14 = 0.46^{\circ} C$

$Δ T_{f} = \frac{100 k_{f} w_{1}}{m_{1} w_{2}}$

$0.46 = \frac{100 \times 3.6 \times 1}{m_{1} \times 100}$

$m_{1} = \frac{36}{0.46} = 78.26 g$

$C = \frac{92.3}{100} \times 78.26 = 72.23 g$

$H = \frac{7.7 \times 78.26}{100} = 6.026 g$ Whole ratio $C = \frac{72.23}{1} = 6.02$

$H = \frac{6.026}{1} = 6.02$ Therefore, the molecular formula is $C_{6} H_{6.}$

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Solutions Question 257

Question: The cryoscopic constant for acetic acid is 3.6 K kg/mol. A solution of 1 g of a hydrocarbon in 100 g of acetic acid freezes at 16.14∘C instead of the usual 16.60∘C . The hydrocarbon contains 92.3% carbon. What is the’molecular formula-

Options:

Answer:

Solution:

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Question: The cryoscopic constant for acetic acid is 3.6 K kg/mol. A solution of 1 g of a hydrocarbon in 100 g of acetic acid freezes at $16.14^{\circ} C$ instead of the usual $16.60^{\circ} C$ . The hydrocarbon contains 92.3% carbon. What is the’molecular formula-