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calculate the freezing poing depression for a solution prepared by dissolving 25

ID: 590289 • Letter: C

Question

calculate the freezing poing depression for a solution prepared by dissolving 25.0g of octane in 175g of benzane calculate the freezing poing depression for a solution prepared by dissolving 25.0g of octane in 175g of benzane an initial mixture of N2 and H2 gases that can be 10. represented as follows: The gases react to form ammonia gas (NH3) as represented by the following concentration profile: Time a. Label each plot on the graph as N2, H2, or NH, and explain your answers. D. Explain the relative shapes of the plots. he n is equilibrium reached? How do you know?

Explanation / Answer

You need to have molal depression in freezing point constant Kf = 4.3 oC/m obtained from internet(please verify it with the given value in your problem).

T = i Kf m

T = depression in freezing point

i = vanthoff factor ( used when there is ionization of solute) our solute is non ionizable and hence i = 1

Kf = freezing point deprsssion constant

m = molality of solute

molar mass of octane =  114.23 g/mol

moles of octane = mass / molar mass = 25g / 114.23 g/mol = 0.2188 mol

mass of solvent = 175g = 0.175 kg

molality = moles of solute / mass of solvent in kg = 0.2188 mol / 0.175 kg = 1.25 m

T = 1 x 4.3 oC/m x 1.25 m = 5.38 oC

Ans = 5.38 oC

N2 + 3H2 -----> 2NH3

concentration of hydrogen should be highest and decreasing over the time to form ammonia and hence it is represented by green line

nitrogen is less than hydrogen but should be decreasing over the course of reaction and hence can be represented by blue line

ammonia concentration should start from zero and increasing, represented by red

equilibrium is reached when all of them have constant concentration,ie. when the lines become parallel to x axis

as y axis represents concentration

comment if you need more help

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