Making Measurements

Question 1

How would you weigh a solid (6 steps)

Answer 1

1. Zero the balance 2. Use a weighing bottle or boat and add in the required mass of solid. 3. Accurately weigh the mass of solid and weighing vessel together and record this information. 4. Empty the solid into the glassware you will be using 5. Accurately reweigh the empty weighing bottle. 6. Subtract the recorded mass for the empty weighing bottle from the mass recorded for the solid and weighing bottle.

Question 2

Why don’t you measure the mass of the weighing bottle empty at the start?

Answer 2

Because some solid may be left in so you need to determine the mass of solid which is added.

Question 3

Why is it important to know how much mass you have added?

Answer 3

To calculate an accurate yield figure

Question 4

What is the name of glassware used to measure the volume of a liquid accurately?

Answer 4

Pipette for a fixed volume Burette for an unknown volume

Question 5

What should you wash the pipette or burette out with before use?

Answer 5

Distilled water and then a small amount of the solution you will accurately measure.

Question 6

Why do you rinse the pipette or burette with the solution you will accurately measure

Answer 6

Any distilled water left in would dilute down the solution.

Question 7

Once you have filled and emptied the pipette into the appropriate glassware what should you do?

Answer 7

Touch it to the side of the beaker to ensure the correct volume is passed on

Question 8

Should you force out the final drop in the bottom of the pipette?

Answer 8

No, its designed to transfer the correct volume and have a drop left in the end

Question 9

What accuracy can a burette measure to?

Answer 9

0.05cm³

Question 10

What do we call the volume of liquid measured with a burette?

Answer 10

The titre

Question 11

Why do we need to use liquids at room temperature when we used a pipette and burette

Answer 11

Thermal expansion would affect the volume of liquid in the glassware if it was too hot or too cold.

Question 12

How many times do you need to find the titre?

Answer 12

Until you have three concordant results so you can calculate an average

Question 13

How could we accurately collect the volume of a gas?

Answer 13

We could use a gas syringe or an inverted measuring cylinder or burette to collect gas

Question 14

Why would a system for collecting gas need to be air tight?

Answer 14

Otherwise gas could be lost to the surroundings and would provide an incorrect measurement of volume