Question

V. (10pts) Calculate the root mean square speed, and the average speed of Neg) on a hot summers day when the temperature is 94.0°C. Express your answers in both meters per second, and miles/hr. VI(15pts) The following picture shows a gas entrapped in a sealed syringe with a movable plunger (aX7 pts) If the trapped gas is a hydrocarbon with empirical formula CH, and if the gas has a volume of 5.58 mL and a mass of 8.98mg at 45.0°C, and I atm pressure, what is the molar mass of the gas and what is its molecular formula? (b) (8pts) in a separate experiment, a gas phase reaction take place in the sealed syringe with the movable plunger. During the course of the reaction, the volume roes from an initial value of 50.0 mL to 75.0 mL at constant pressure and temperature of the reactions given in the following list, which took place? Indicate how you arrived at this result. (a) 2A(g) + B(g) ----> A,B(g) (b) A(g) + B(g) --> AB(B) (c) 2 AB(g) ---> A(g) + B (g) (d) 2 AB (g) - > Arg) + 2 B (g) (e) 2 A (g) + 4 B(g) ----> 4 AB(g) (Problem adapted from Moor, Stanistky, and Jurs Chemistry 2 ed chapter 10)

Answer 1

Q VI (a)

PV = nRT

n = 1atm×5.58×10^-3L/(0.0821atm.L/K.mol × 318.15K) = 2.13628×10^-4 mol

Molar mass of hydrocarbon = 8.98×10^-3g/(2.13628×10^-4mol) = 42.0356g/mol

Molecular formula be (CH₂)_x

x = 42.03/14 = 3

Molecular formula of hydrocarbon is  C₃H₆ (propene )

(b)

At same pressure and temperature, volume occupied by gas is directly proportional to the number of moles of gas .

As the volume of syringe increases from 50.0ml to 75.0ml , the chemical reaction would have resulted into more number of gaseous compounds in product side . Hence

(d) 2AB₂(g) $\rightarrow$ A₂(g) + 2 B₂(g) (Answer)