Question

How would your calculations for the mass of Mg metal present in the sample have been affected (if at all) by the fallowing observations? Clearly explain your reasoning fo reach answer.

1. Your instructor had inverted two numbers when reading the pressure and reported wha the barometric pressure was 754 torr when in fact the correct room pressure was 745 torr.

2.Your partner had tightly held the gas-filled porition 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

Answer 1

Answer – We are given the observation and need to find out the what is the effect on the calculations for the mass of Mg metal present in the sample.

This is experiment in which there is reaction of Mg metal with HCl and evolving H₂ gas.

1)If your instructor had inverted two numbers when reading the pressure and reported what the barometric pressure was 754 torr when in fact the correct room pressure was 745 torr, then there is found to be more moles of H₂ gas and hence there is more moles of Mg found. So as the more moles of Mg metal found the mass of Mg found the more than actual.

2) If 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, then we found to be incorrect volume of gas, means there was found low volume of gas and which show the low moles of gas and directly found the low moles and mass for Mg metal.

3) If an edge of the Mg ribbon was outside the buret and some hydrogen may have escaped, then there is found to be less mass of Mg, since when there is Mg ribbon was outside the buret there is not complete reaction and also formed gas escaped,so we found the volume of gas is low and hence low moles, so low moles for Mg metal and we will found the low mass.

4) If you did not correct for the difference in water levels, then there found to be incorrect volume of gas and which is directly proportional with mass of Mg metal =,so mass of Mg calculation also found incorrect.

5) If you added rather than subtracted the vapor pressure of water to your final pressure reading, then there got more pressure than actual and that affect the moles of gas. There were found more moles of gas than actual and we know moles of gas more means moles Mg metal more and more mass of Mg metal than actual