An ideal solution is formed from a mixture of the nonvolatile solute urea, CO(NH

Question

An ideal solution is formed from a mixture of the nonvolatile solute urea, CO(NH_2)_2, and methanol, CH_3 OH. The vapor pressure of pure methanol at 20 degree C is 89 mmHg. If 5.0 g of rea is mixed with 36.0 g of methanol, calculate the vapor pressure of the methanol solution. A) 6.1 mmHg B) 78 mm Hg C) 71 mmHg D) 18 mmHg E) 83 mmHg The average rate of disappearance of ozone in the reaction 2O_3 (g) rightarrow 3O_2 (g) is found to be 7.91 times 10^-3 atm over a certain interval of time. What is the rate of appearance of O_2 during this interval? A) 11.9 times 10^-3 atm/s B) 7.91 times 10^-3 atm/s C) 5.27 times 10^-3 atm/s D) 247 times 10^-3 atm/s E) 20.9 times 10^-3 atm/s Consider the following rate law: Rate = k[A]^n [B]^m How are the exponents n and m determined? A) by using the balanced chemical equation B) by using the subscripts for the chemical formulas C) by using the coefficients of the chemical formulas D) by educated guess E) by experiment

Explanation / Answer

Q12.

Apply colligative properties

dP = xsolute * Psolvent

x solute = mol of urea / total mol

mol of urea = mass/MW = 5/60 = 0.08333 mol o furea

mol of methanol = mass/MW = 36/32 = 1.125 mol

x-solut e= 0.08333 /(1.125 +0.08333 ) = 0.068962

now

dP = 0.068962*89

dP = 6.137618 mm Hg

P mix = P-dP = 89-6.137618

P mix = 82.862 mm Hg

choose E

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