Question

1. Silver oxide decomposes when heated:

2 Ag2O(s)4 Ag(s) + O2(g)

If 5.76 g of Ag2O is heated and the O2 gas produced by the reaction is collected in an evacuated flask, what is the pressure of the O2 gas if the volume of the flask is 0.65 L and the gas temperature is 25 °C?
(a) 0.94 atm (b) 0.039 atm (c) 0.012 atm (d) 0.47 atm (e) 3.2 atm

2. In the first step of the industrial process for making nitric acid, ammonia reacts with oxygen in the presence of a suitable catalyst to form nitric oxide and water vapor:

4 NH3(g) + 5 O2(g) 4 NO(g) + 6 H2O(g)
How many liters of NH3(g) at 850 °C and 5.00 atm are required to react with 1.00 mol of O2(g) in this reaction?

Answer 1

2 Ag2O ---------------> 4 Ag + O2

no of moles = mass / molar mass

for Ag2O = 5.76g / 231.735 g/mol => 0.02485 moles

2 moles Ag2O -------------------> 1 mol O2

0.02485 moles -------------------->

=> 0.02485 * 1 /2 => 0.012427 moles

moles (n) = 0.012427 moles

volume V = 0.65 L

temperature = 25 c = 298 K

R = 0.0826 L atm / K mol

using ideal gas equation

PV = nRT

P = nRT / V

P = 0.012427 * 0.0826 * 298 / 0.65

P = 0.47 atm

answer => d ) 0.47 atm

2) from the balanced equation

5 mol O2 ------------------> 4 mol NH3

1 mol O2 ------------------> ?

=> 1 * 4 / 5 => 0.8 moles i.e n

p = 5.00 atm

T = 850c = 1123.15 K

V = nRT / P

V = 0.8 * 0.0826 * 1123.15 / 5

V = 14.843 liters

answer => volume = 14.843 liters