To measure the amount of oxygen produced in the reaction O2

To measure the amount of oxygen produced in the reaction, O2 is collected over water, as shown below. 2 KC1O3(s) 2 KCI(s) +3 02(g) of 02 produced by the Calculate the mass decomposition of KCIO3 when 831 mL of O2 is collected over water at 30.0°C and 1.015 atm. (The vapor pressure of water at 30.0°C is 31.8 torr.)

Solution

pH2O = 31.8 torr

= 31.8/760 atm

= 0.0418 atm

we have for O2

P = 1.015 atm - 0.0418 atm

= 0.973 atm

V = 831.0 mL

= (831.0/1000) L

= 0.831 L

T = 30.0 oC

= (30.0+273) K

= 303 K

find number of moles using:

P * V = n*R*T

0.973 atm * 0.831 L = n * 0.08206 atm.L/mol.K * 303 K

n = 3.252*10^-2 mol

Molar mass of O2 = 32 g/mol

we have below equation to be used:

mass of O2,

m = number of mol * molar mass

= 3.252*10^-2 mol * 32 g/mol

= 1.041 g

Answer: 1.04 g