How would a calculation for the mass of Mg metal present in a sample be affected

Question

How would a calculation for the mass of Mg metal present in a sample be affected by the following
You do not need numbers to answer the following, merely explain how calculations x would differ to become calculations y

POST-LAB QUESTIONS How would your calculation for the mass of Mg metal present in the sample have been a (if at all) by the following observations? Clearly explain your reasoning for each answer ffected 1. Your instructor had inverted two numbers when reading the pressure and reported that the barometric pressure was 754 torr when in fact the correct room pressure en in fact the correct room pressure was 745 torr. 2. Your partner had tightly held the gas-filled portion of the buret in his hand while you were trying to determine the difference in the water levels. 3. An edge of the Mg ribbon was outside the buret and some hydrogen may have escaped 4. You did not correct for the difference in water levels 5. You added rather than subtracted the vapor pressure of water to your final pressure reading.

Explanation / Answer

1)

If P was lower, then there was less mol of gas than calculated, therefore, you will have the

mass = mol*MW

since mol real is less, and mol read is high, expec a higher mass than the real mass

2)

None, the buret has fixed volume, so won't change its volume with compression

3)

IF H2 escaped, then you will measure a lower Volume of H2, therefore, less moles of H2, and relate sto lower Mg which is false

4)

The volume will be wrongly read, therefore volume of H2, is less, and Mg is therefore less than real

5)

If you add vapor pressure, the equation has a higher pressure, therefore a higher volume which is false

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