Introduction to Lab Techniques

Part 1: Burets and Titrations

Set up the washed and cleaned burette using the clamp on the stand and fill it up all the way. Dispense the correct amount of water (in mL) from the burets into your 50.0 mL beaker.  Please ensure that you are using the correct significant figures.

Using a buret, transfer water into an empty beaker.  Record the necessary weights.  Be sure to record initial and final volumes for the buret (in mL) to the correct number of significant figures. Recreate the table below in your lab notebook to record observations. Don’t forget the units and watch the significant figures!!!

	Mass recorded of 50 mL beaker without water (g) (Initial mass)	Mass recorded of 50 mL beaker with water (g) (final mass)	Mass of water
Empty Beaker
5 mL water total
10 mL water total
15 mL water total

 

Buret initial volume: _______________

Buret final volume: ________________

Part 1 Questions:

1. How many significant figures should be used with a buret? Why? Explain your reasoning.
2. What is the mass of 1 mL of water based on the density that was calculated in this section?
3. Should the buret be washed when changing solutions,? Why?
4. What is the procedure for washing a burette when changing solutions? Why?

Part 2: Volumetric Pipettes

Measure the following using volumetric pipettes and transfer them to a pre-weighed 50 mL beaker. Recreate the table below in your lab notebook to record detailed observations.

Don’t forget the units and watch the significant figures!!!

Solution	Mass recorded of 50 mL beaker without water (g) (Initial mass)	Mass recorded of 50 mL beaker with water (g) (final mass)	Mass of water (g)
5 mL water
10 mL water
15 mL water

Part 2 Questions:

1. What is the procedure to get the bottom of the meniscus to the volumetric line of the pipette?
2. When is it appropriate to stop brining liquid into the pipette? Explain your reasoning.
3. How many significant figures should be used with a pipette? Why?
4. What is the mass of 1 mL of water based on the density that was calculated in this section?
5. What is the procedure for washing a pipette when changing solutions? Why?
6. Should the pipette be washed when changing solutions,? Why?

Part 3: Graduated Cylinder

Measure the following volumes in a pre-weighed 50 mL beaker (use the markings on the beaker itself to measure the volume. Recreate the table below in your lab notebook to record detailed observations.

When you make the same measurement three times i.e. the three measurements are exactly identical to one another In how you made them, this is referred to as “making the measurement in triplicate”. Remember this terminology for future labs.

Don’t forget the units and watch the significant figures!!!

Solution	Mass recorded of 50 mL beaker without water (g) (Initial mass)	Mass recorded of 50 mL beaker with water (g) (final mass)	Mass of water (g)
10 mL water
10 mL water
10 mL water

 

Part 3 Questions:

1. How many significant figures should be used with this graduated cylinder? Why?
2. What is the mass of 1 mL of water based on the density that was calculated in this section?
3. What is the procedure for washing a graduated cylinder when changing solutions? Why?
4. When changing solutions, how should the graduated cylinder be washed? Why?
5. Is making measurements in triplicate a good practice in the lab? Why or why not? Explain your reasoning.

Part 4: Beakers

Measure the following volumes in a pre-weighed 50 mL beaker (use the markings on the beaker itself to measure the volume. Recreate the table below in your lab notebook to record detailed observations.

When you make the same measurement three times i.e. the three measurements are exactly identical to one another In how you made them, this is referred to as “making the measurement in triplicate”. Remember this terminology for future labs.

Don’t forget the units and watch the significant figures!!!

Solution	Mass recorded of 50 mL beaker without water (g) (Initial mass)	Mass recorded of 50 mL beaker with water (g) (final mass)	Mass of water (g)
10 mL water
10 mL water
10 mL water

 

Part 4 Questions:

1. How many significant figures should be used with a beaker? Why?
2. What is the mass of 1 mL of water based on the density that was calculated in this section?
3. What is the procedure for washing a beaker when changing solutions? Why?
4. When changing solutions, how should the beaker be washed? Why?

Calculations

Make sure you are watching the sig figs and units when doing calculations.

Determine the density of water for each of your observations.

Redraw the tables for parts 1, 2, 3 and 4 and add a column at the end for density of water.

For each part show one sample calculation on how you calculated the density of water and then fill the remaining values into the table you created directly.

Make sure you label the tables and the columns and rows of the tables clearly.

DON’T FORGET THE UNITS!!!

Calculate the average (mean) density to Parts 1, 2, 3 and 3 individually (for each part – so you should have an average (mean) density for Part 1, average (mean) density for Part 2 etc….). Show your work for how you calculated the density for each part separately (Parts 1, 2, 3 and 4)

Calculate the standard deviations for the density values you calculated in Part 3. Repeat for the values of density you calculated in part 4.

Present your results in the form of a table. Create a table containing the name of the lab equipment you used to measure volume, the average (mean) density of water and the standard deviation (for parts 3 and 4 only, leave blank for parts 1 and 2 or say not calculated).

Start thinking about what these numbers mean because you will have to explain it in your lab report.