Core Practical 1

Question 1

What is molar volume of gas?

Answer 1

Volume occupied by one mole of a gas at room temperature and pressure

Question 2

How is percentage uncertainty effected when a apparatus with double the volume is used?

Answer 2

Halves the % volume uncertainty
Volume of gas is doubled so mass uncertainty halves

Question 3

What changes with the syringe when there is a gas leak?

Answer 3

The syringe plunger will not go back to 0 when released
The molar mass will decrease because air will have a lower molar mass than CO2

Question 4

What is the effect of a decrease in temperature on molar mass?

Answer 4

Increase in molar mass as at lower temp there is a more mass for the same volume

Question 5

Why should gas be dry in this experiment?

Answer 5

The gas is a mixture so would decrease molar mass. Water vapour decreases molar mass

Question 6

Why is a small pinch of the calcium carbonate added to the acid

Answer 6

To saturate the solution.

Question 7

Why could there be a possible difference between theoretical calculation and actual value for hydrogen gas obtained?

Answer 7

Hydrogen gas may escape from the apparatus. so use a sealed apparatus with gas syringe or conical flask

Magnesium ribbon may become covered in oxide. Clean abrasively or with abrasive to remove oxidation

Mass of magnesium may be less than 0.04g so too small to be measured so use a more accurate or precise balance or a larger mass