Potassium chromate, a bright yellow solid, is produced by the reaction of solid

Question

Potassium chromate, a bright yellow solid, is produced by the reaction of solid chromite ore (FeCr2O4)with solid potassium carbonate and gaseous oxygen at high temperatures. The other products of the reaction are solid iron (III) oxide and gaseous carbon dioxide. In an experiment, 169 Kg of chromite ore, 298 Kg of potassium carbonate and 75.0 Kg of oxygen are sealed in a reaction vessel and reacted at a high temperature. The amount of potassium chromate obtained was 194 Kg. Calculate the percent yield of potassium chromate

Explanation / Answer

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

Percent yield = ( actual / theoretical yield) x 100

= ( 194 / 292.7) x 100

= 66.3 %

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