Consider the ideal gas law equation used to calculate the moles of H2 (#6 above)
ID: 531078 • Letter: C
Question
Consider the ideal gas law equation used to calculate the moles of H2 (#6 above): PV = nRT n = PV/RT
Referring back to this equation, explain what effect (increase, decrease, no change) the following proceduralerrors have on the value of n (moles of hydrogen gas):
a. The Mg did not react completely because a small piece floated out of the tube.
b. The pressure of the hydrogen gas was recorded without subtracting the vaporpressure of water.
c. Some of the water in the tube was allowed to leak out through the hole in the stopper beforemeasuring the volume.
d. The pressure was recorded based on the room temperature only, rather than averaging the threedifferent temperatures.
Explanation / Answer
(a) Since Mg is not reacted completely, it produces less number of moles of Hydrogen gas.
(b) Since pressure due to water vapour is not substracted, it shows higher pressure of H2 and hence more number of moles of H2 gas.
(c) It give less number of moles of hydrogen gas.
(d) If average temp. is hihger than the room temp. it gives more number of moles of H2 gas, if the temp. is lower than the room temp. , it gives less number of moles of H2 gas.