# Practical Skills Flashcards

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1
Q

What is the method of gas collection?

A

Inverted measuring cylinder filled with water in a trough of water, or a gas syringe if the gas is water soluble.

2
Q

What is the method to record the mass lost and why can it be used?

A

A reaction which produces a gas will lose mass, so the mass lost can be used to the measure the mass of gas produced?

3
Q

When can you not use the mass lost method?

A

If the RFM of the gas is too low, e.g. hydrogen.

4
Q

What is gravimetric?

A

Heating and weighing a solid in a crucible. You may need to lift lid to let gases in or out, break up solid to make sure it all reacts or heat to constant mass to ensure it has finished reacting.

5
Q

What equipment is used in titration?

A

6
Q

What do you need to remember to do when doing a titration?

A

Use solids of known RFM to make standard solutions - avoid solids that absorb or lose water. Repeat until 2 concordant results obtained.

7
Q

What is measured when doing an enthalpy change experiment and how can you calculate the temperature change?

A

Measure the temperature change. Extrapolate to obtain maximum temperature, particularly if reaction is very exothermic as more heat energy will be lost at the start of the reaction.

8
Q

What is uncertainty?

A

Half a division.

9
Q

What is percentage uncertainty when two measurements taken?

A

(uncertainty x2) / measurement x100

10
Q

How can you reduce uncertainty?

A

Measure larger quantity or use apparatus with smaller divisions.

11
Q

With gas collection how can you improve the error in which less gas is collected?

A

Use specimen tube in flask and mix after bung is in place.

12
Q

How can you improve the error that gas is lost due to dissolving in water?

A

Use a gas syringe.

13
Q

What does the replacement of the bung in gas collection result in and how can this be improved?

A

More gas is collected. To improve this measure how much and subtract from volume measured.

14
Q

How can you correct the standard conditions error in gas collection?

A

Measure temperature and pressure and use ideal gas equation to adjust.

15
Q

What are the errors in gravimetric?

A

Some solid is lost when lid lifted which results in lower mass recorded. Not all the solid has reacted. To improve this heat to constant mass.

16
Q

What are the errors in enthalpy change experiments?

A

Heat loss = lower temp change measured.
Assuming mass of solution is equivalent to initial volume.
Non standard conditions.

17
Q

How can the errors in enthalpy change be improved?

A

Use a lid, insulate or use draught exclusion.

Use the final mass of the reaction as m in mcΔt.

18
Q

What are the errors in enthalpy change of burning fuels?

A

Incomplete combustion. Evaporation of water - can be improved by putting a lid on the calorimeter.