What is the molar mass of a nonelectrolyte if 5.12 grams of it is dissolved in 2
ID: 490450 • Letter: W
Question
What is the molar mass of a nonelectrolyte if 5.12 grams of it is dissolved in 27.5 grams of chloroform solvent to form a solution that has a boiling point of 67.54 degree C? The boiling point of pure chloroform is 61.70 degree C and the boiling point elevation constant. k_b, is 3.63 degree C/m Why does the temperature of a substance stay constant during a phase change such as vaporization? The reaction of NO(g) and O_2(g) produces NO_2(g) + O_2 rightarrow NO_2(g) The reaction is second-order with respect to NO(g) and first-order with respect to O_2(g). At a given temperature, the rate constant, k, equals 6.7 times 10^3 M^-2 s^-1. What is the rate of reaction when the initial concentrations of NO and O_2 are both 0.015 M?Explanation / Answer
21) The elevation in boiling point = 67.54 -61.70 = 5.84
Given kb = 3.63 C/m
mass of solute = 5.12g
mass of solvent = 27.5g
W know elevation in boiling point = Kb x m
= kb x (mass of solute/molar mass) (1000/ mass of solvent g)
thus 5.84 = 3.63 x (5.12/M) (1000/27.5)
and molar mass M = 115.72 g/mol
22) During the phase change (melting/evaporation) the heat supplied is used to overcome the intermolecular attractions between the molecules that is the latent heat of phase change, so the temperature of the system does not change inspite of continuous supply of heat.
23) From the given data , rate expression is
Rate = k [NO]2{O2}
Given k = 6.7x 103 M-2s-1 and [NO] =[O2] = 0.015M
Thus initial rate of reaction = 6 .7x 103 M-2s-1 x(0.015)2 (0.015)
= 2.26x 10-2 M/s
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