Question

What effect would each of the following errors have on the determined concentration of the unknown acid? (would the calculated value be too high, too low, or unchanged?) explain

a) the mass of oxalic acid was recorded too high.
b) the unknown acid was added to a flask containing 5mL of water.
c) the initial volume in the standardization was recorded too low.
d) the initial volume in the determination of the unknown was recorded low.

Answer 1

Measurement errors in titration can significantly alter the determined concentration of an unknown acid. Overestimating the mass of oxalic acid or the initial volume in standardization or determination causes the calculated concentration of the unknown acid to be too low or too high, respectively. Diluting the unknown acid with a known volume of water does not affect the concentration if accounted for in calculations.

Step-by-step explanation:

When determining the concentration of an unknown acid through titration, any errors in measurement or procedure can impact the calculated concentration. Let's consider the following errors:

1. Mass of oxalic acid recorded too high: If the mass of oxalic acid used for standardization is recorded as being higher than it is, the calculated concentration of the acid would be too low. This is because the titration would suggest that more moles of acid are present which would require more base to neutralize, skewing the concentration calculation.
2. Unknown acid added to a flask with water: Diluting the unknown acid with water before titration should not change the calculated concentration, as long as the total volume is accounted for in the calculations, since the number of moles of acid present remains the same.
3. Initial volume in the standardization recorded too low: Under-recording the initial volume of the solution during standardization would lead to a higher calculated concentration of the standard solution because the concentration calculation is based on the ratio of moles of solute to the volume of solution. Consequently, this would also affect the concentration calculated for the unknown acid, making it appear too high.
4. Initial volume in the determination of the unknown recorded low: Similar to the standardization error, if the initial volume is recorded as less than the actual amount, then the concentration of the unknown will be calculated as higher than it should be, because the mole-to-volume ratio would be incorrectly increased.

Answer 2

Errors in titration can significantly affect the calculated concentration of an unknown acid. Recording too high mass of oxalic acid or too low initial volume can lead to underestimating and overestimating the acid concentration, respectively.

Step-by-step explanation:

When conducting a titration to determine the concentration of an unknown acid, certain errors can affect the accuracy of the calculated concentration. Let's examine the effects of the listed errors:

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• a) If the mass of oxalic acid used as a standard in the titration is recorded too high, the calculated concentration of the unknown acid will be too low. The reason is that more moles of the standard would be presumed to react with the unknown acid, suggesting a higher than actual neutralization capacity.
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• b) Adding the unknown acid to a flask containing 5mL of water should not change the concentration of the acid directly. However, it is the volume of titrant added that determines the end point of the titration, not the volume of acid present initially.
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• c) If the initial volume in the standardization is recorded too low, the calculated concentration of the standard solution would be too high. This would lead to an overestimation of the unknown acid's concentration since it would appear that it took more standard substance to neutralize it.
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• d) The initial volume in the determination of the unknown was recorded low will similarly result in a too high calculated concentration of the unknown. The lower initial volume suggests a more concentrated acid than is actually present.