What would be the effect on the percent Pb reported in the analysis if: a. the...

What would be the effect on the percent Pb reported in the analysis if:

a. the precipitate of PbCrO4 was not completely dried?

b. some of the unknown lead salt was spilled while transferring the sample to the beaker?

c. the orange precipitate of PbCrO4 was not completely transferred to the filter paper?

Solutions

Expert Solution

(a) If the given precipitate is not fully dry then when we measure the mass, we will get a higher mass of PbCrO₄ (s) than the actual yield as currently we are measuring the mass of PbCrO₄ (s) plus the water. A higher mass of PbCrO₄ (s) will result in calculating higher number of moles of PbCrO₄ (s), which will be then converted into higher moles in the mixture. In the last we end up calculating that the mass percent of Pb(s) is higher than it actual is.

(b) When the unknown lead salt was spilled while transferring to the beaker, then there was found less amount of PbCrO₄ and it gives less amount of moles and concentration, so PbCrO₄ also got the lesser in number and molarity got low.

(c) the orange precipitate of PbCrO4 was not completely transferred to the filter paper then mass percent of Pb will not have any effect only the overall yield will be less since the reaction has been completed and only the weight is found to be less

queen_honey_blossom answered 2 years ago

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