Question

1. To what Celsius temperature must 67.5 mL of krypton gas at 17.0°C be changed so the volume will triple? Assume the pressure and the amount of gas are held constant. Enter your answer to four significant figures.

2. Calculate the volume of 50.5 g of C2H2 gas at standard temperature and pressure (STP). Use a molar mass with at least as many significant figures as the data given.

3. Calculate the volume of 41.5 g of NH3 gas at standard temperature and pressure (STP). Use a molar mass with at least as many significant figures as the data given.

Answer 1

1)

Given:

Ti = 17.0 oC

= (17.0+273) K

= 290 K

Vi = 67.5 mL

Vf = 3*Vi = 3*67.5 = 202.5 mL

use:

Vi/Ti = Vf/Tf

67.5 mL / 290.0 K = 202.5 mL / Tf

Tf = 870 K

Tf = 597 oC

Answer: 597 oC

2)

Molar mass of C2H2,

MM = 2*MM(C) + 2*MM(H)

= 2*12.01 + 2*1.008

= 26.036 g/mol

mass(C2H2)= 6.8 g

number of mol of C2H2,

n = mass of C2H2/molar mass of C2H2

=(6.8 g)/(26.036 g/mol)

= 0.2612 mol

Given:

P = 1.0 atm

n = 0.2612 mol

T = 273.0 K

use:

P * V = n*R*T

1 atm * V = 0.2612 mol* 0.0821 atm.L/mol.K * 273 K

V = 5.85 L

Answer: 5.85 L

I am allowed to answer only 1 question at a time