Answer to Question #186352 in General Chemistry for Miranda

Question

Potassium chromate, a bright yellow solid, is produced by the reaction of solid chromite ore (FeCr2O4)(FeCr2O4) with solid potassium carbonate and gaseous oxygen at high temperatures. In an experiment, 169000 g of chromite ore, 298000 g of potassium carbonate and 75000 g of oxygen are sealed in a reaction vessel and reacted at a high temperature. The amount of potassium chromate obtained was 194000 g. 

FeCr2O4 + K2CO3 + O2 -> K2CrO4 + Fe2O3 + CO2

Find the following:

1) limiting reactant

2) theoretical yield

3) percent yield

with solution if possible

Answer 1

The balanced reaction is : 2 FeCr2O4 + 4 K2CO3 + 5 O2 --------> 4 K2CrO4 + 2 FeO3 + 4 CO2

molar mass (g/mol) 224 138 32 194

from the balanced reaction ,

2 mol=2x224=448 g of FeCr2O4 reacts with 4mol=4x138=552 g of K2CO3 and 5 mol= 5x32=160 g of O2

(OR) 448 kg of FeCr2O4 reacts with 552 kg of K2CO3 and 160 kg of O2

169 kg of FeCr2O4 reacts with M kg of K2CO3 and N kg of O2

M = ( 169x552)/448 N = ( 169x160)/448

= 208.2 kg = 60.3 kg

So all the mass of potassium chromite completly reacted so it is the limiting reactant.

from the balanced reaction,

2 mol=2x224=448 g of FeCr2O4 produces 4 mol = 4x194=776 g of K2CrO4

(OR) 448 kg of FeCr2O4 produces 776 kg of K2CrO4

169 kg of FeCr2O4 produces Y kg of K2CrO4

Y = (169x776) / 448

= 292.7 kg --------> this is the theoretical yield

3)Percent yield = ( actual / theoretical yield) x 100

= ( 194 / 292.7) x 100

= 66.3 %