A. Would your calculated normality be increased, decreased or unchanged if the f

Question

A. Would your calculated normality be increased, decreased or unchanged if the following problem occurred. Give reasons.

1. The Mohr's salt you used contained small amounts of non hydrated water.

2. 200 ml. of water were used to dissolve the Mohr's salt sample in place of the required amount.

3. The endpoint was carried to a deep red in place of the normal light pink.

4. The phosphoric acid was not added as the endpoint was approached.

B. Write balanced equations to illustrate what would happen is in the standardization of the KMnO4 the acid (H2SO4) was omitted. How would you note this error?

Explanation / Answer

A. Would your calculated normality be increased, decreased or unchanged if the following problem occurred. Give reasons.

1. The Mohr's salt you used contained small amounts of non hydrated water.

solution :- If the unhydrated water is present then it will give the higher mass of the salt which leads to more moles of salt so it will have higher concentration.

2. 200 ml. of water were used to dissolve the Mohr's salt sample in place of the required amount.

solution :- If the water used is not same as the water needed to required to make the solution then it will decrease the concentration of the solution.

3. The endpoint was carried to a deep red in place of the normal light pink.

Solution :- End point was carried to deep red color means the titration is overshot so this will give the increase in the concentration.

4. The phosphoric acid was not added as the endpoint was approached.

Solution :- if the phosphoric acid was added then it will not show the color change this will lead to overshot in the titration which will lead to increase in the concentratio.

B. Write balanced equations to illustrate what would happen is in the standardization of the KMnO4 the acid (H2SO4) was omitted. How would you note this error?

solution :-

Balanced equation is

2KMnO4 +3H2SO4 +5H2C2O4.2H2O ------ > K2SO4 + 2MnSO4 + 18H2O + 10 CO2

so if the H2SO4 is ommitted then the reaaction would not go to the completion therefore it will not show change in the color.

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