Question

5. Two chemicals, A and B, are combined, forming chemical C. The rate of the reaction is jointly proportional to the amounts of A and B not yet converted to C. Initially, there are 50 grams of A and 80 grams of B, and, during the reaction, for each two grams of A used up in the conversion, there are three grams of B used up. An experiments show that 100 grams of C are produced in the first ten minutes. After a long period of time, how much of A and of B remains, and how much of C has been produced?

Answer 1

For each 2 g of A, 3 g of B is used up.

Hence, for 50 g of A, amount of B needed = 50 x (3/2) = 75 g of B. So, A is the limiting reactant and B is in excess.

According to the law of conservation of mass, amount of produt formed is the sum of amounts of the reatants reacting.

Hence, 50 g of A reacts with 75 g of B, to give 125 g of C.

In the first 10 min, 100 g of C is formed, indicating that the reaction is ompleted to a large extent. Assuming that the reaction reaches completion, after the long period of time, all of A would have reated with only 75 g of B to give 125 g of C.

After a long period of time,

Amount of A remaining = 0

Amount of B remaining = 80 - 75 = 5 g

Amount of C produced = 125 g.