Answer to Question #55722 in General Chemistry for tracy guido

Question

In a lab experiment finding the limiting reactant with Sodium bicarbonate and citric acid, it was found that the limiting reactant was sodium bicarbonate. If I have to devise an experiment to test my conclusion to which reactant is limiting do I add sodium bicarbonate or citric acid?

I added more sodium bicarbonate and it began to react and fizz again, does this prove that citric acid is in excess?

Part two I had to make a mixture that citric acid was the limiting reactant.
I did not have time to finish the lab -- What experiment would I devise to test my conclusion to that citric acid was limited. Would I add citric acid? what would happen?

Answer 1

There are three possibilities:
1. Equivalent quantities of citric acid and bicarbonate (no acid or bicarbonate remains unreacted after reaction);
2. Excess of bicarbonate - citric acid is limiting reagent (some bicarbonate remains unreacted after reaction);
3. Excess of acid - bicarbonate is limiting reagent (some acid remains unreacted after reaction).
In first case addition of acid or bicarbonate will not change anything;
In second case if you add some acid, reaction mixture will began to react and fizz again.
In third case if you add some bicarbonate, reaction mixture will began to react and fizz again.

So, we can conlude:
Limiting bicarbonate can be observed by addition of bicarbonate;
Limiting acid can be observed by addition of acid.

In your part two experiment you have to add some citric acid and observe the neutralization reaction with CO2 evolution.