Question

1. In a bomb calorimeter, reactions are carried out

a. at 1 atm pressure and 25

Answer 1

1) In a bomb calorimeter , reactions are carried out at (e) constant volume

Bomb calometers are used to measure heta of combustion of reactions and has to withsatnd high pressures.It is a closed container type structure made of stainless steel which collects the heat generated in the reaction at constant volume.

2) Let mass of Nitrogen = x

Thus, mass of carbon dioxide = (26.4 - x) g

Molar mass of nitrogen = 28 g/mole

molar mass of carbon dioxide = 44 g/mole

Thus, moles of nitrogen in the sample = mass/molar mass = x/28

moles of carbon dioxide in the mixture = mass/molar mass = (26.4-x)/44

Now, Total moles of gases in the mixture = (x/28) + {(26.4-x)/44} = (16x + 739.2)/1232 = (x + 46.2)/77

Now, pressure of the gas mixture = 833.7 mm of Hg = (833.7/760) = 1.1 atm

Now, Applying Ideal Gas Equation , i.e. P*V = n*R*T ;

where P = pressure in atm ; V = volume in litres ; R = Universal gas constant = 8.314 atm*L/(mole*K) ; T = temperature in kelvin = 273 + 44.6 = 317.6 K & n = moles of the gases ; we get

1.1*16.6 = {(x+46.2)/77}*0.0821*317.6

or, 7.72 = x

Thus, mass of nitrogen = 7.72 g

mass of carbon dioxide = 26.4 - x = 18.68 g

Hence moles of nitrogen = 7.72/28 = 0.256

moles of carbon dioxide = 18.68/44 = 0.425

Thus, mole fraction of nitrogen = moles of nitrogen/(moles of nitrogen+moles of carbon dioxide) = 0.376

Thus, the correct option is :- (b)