0.10 Bonding 07  (Page 3/3)

Choose an input, click on the red box that corresponds to the port that your conductivity sensor is connected to. Choose 20,000 microseconds

“Choose a Sensor”, click radial button that says Conductivity Probe. Click next.

Click“Perform New Calibration”

Click“Add Calibration Point”place the conductivity probe in the non-conductive standard solution, while swirling wait until the value is constant and then enter 0.0 into the“Actual Value”box in MicroLab and hit“ok”.

Again, Click“Add Calibration Point”place the conductivity probe in the conducting standard solution, while swirling wait until the value is constant and then enter 1020 into the“Actual Value”box in MicroLab and hit“ok”. Repeat for 3860 as the Actual Value.

Under Curve Fit Choices , click on“First order (linear)”and then“Accept and Save this Calibration”, when prompted to“Enter the units for this calibration”, leave as is and click ok, save as your name-experiment-date. Click finish.

In the sensor area, left click on the conductivity icon and drag it to the Y-axis over“data source two”, also click and drag to column B on the spreadsheet and also click and drag to the digital display window.

When ready to obtain data, click start.

This is very important: Be sure to thoroughly since the probe with DI water between every use.

Beginning with the tap water, measure the conductance of each of the following solutions. Using the information provided in the lab manual, classify each solution as a non-, weak, or strong electrolyte. For those solutions that are electrolytes, record the ions present in solution.

Part iii. electrolyte strength and reaction rate

Chemicals

• calcium carbonate powder - shake once
• 1 M HCl - stopper it
• 1 M ${\text{HC}}_2{H}_3{O}_2$
• 0.5 M $H_2{\text{SO}}_4$
• Test tube gas collection apparatus - end at 20mL

Measure 2 g of powdered calcium carbonate ( ${\text{CaCO}}_3$ ) onto a piece of weigh paper. Obtain 30 mL of 1 M HCl in a graduated cylinder. Pour the acid into the test tube apparatus. Add the calcium carbonate to the acid and QUICKLY stopper the tube to begin collecting gas. Record the time it takes to collect 20 mL of gas. The acid may react very fast with the ${\text{CaCO}}_3$ generating the gas very rapidly. Clean out the test tube apparatus and repeat the experiment using 1 M ${\text{HC}}_2{H}_3{O}_2$ and 0.5 M $H_2{\text{SO}}_4$ .

Part iv. chemical reactions

Chemicals

• 0.01 M calcium hydroxide, $\text{Ca}(\text{OH}{)}_2$
• Plastic straws

Obtain ~20 mL of saturated calcium hydroxide solution. Make sure it is clear and colorless. Place the conductivity probe in the solution and begin monitoring it conductivity. With your straw, slowly exhale into the solution. Note any observations in the solution and the conductivity.

Pre-lab 5: bonding 07

(total 10 points)

Hopefully here for the Pre-Lab

Name(Print then sign): ___________________________________________________

Lab Day: ___________________Section: ________TA__________________________

This assignment must be completed individually and turned in to your TA at the beginning of lab. You will not be allowed to begin the lab until you have completed this assignment.

Part i. bonding of chemicals in solution

• Write out the formulas of the following acids:

• phosphoric ____________________

• perchloric ____________________

• nitric ____________________

• sulfuric __________________

• hydrochloric ____________________

• acetic ____________________

• Write out the formulas of the following bases:

• calcium hydroxide ____________________

• potassium hydroxide ____________________

• sodium hydroxide ____________________

• ammonia ____________________

• Write out the formulas of the following salts:

• potassium chromate ____________________

• potassium sulfate ____________________

• copper(II) nitrate ____________________

• calcium carbonate ____________________

• potassium iodide ____________________

Report 5: bonding 07

Hopefully here for the Report Form

Note: In preparing this report you are free to use references and consult with others. However, you may not copy from other students’work (including your laboratory partner) or misrepresent your own data (see honor code).

Name(Print then sign): ___________________________________________________

Lab Day: ___________________Section: ________TA__________________________

Part i. predicting bond type through electronegativity differences.

Part ii. weak and strong electrolytes

1. Why do we use deionized water instead of tap water when making solutions for conductivity measurements?

Part iii. electrolyte strength and reaction rate

2. Time to collect 20 mL of gas using 1 M HCl _______________________. Write the reaction of HCl with ${\text{CaCO}}_3$ .

3. Time to collect 20 mL of gas using 1 M ${\text{HC}}_2{H}_3{O}_2$ _______________________. Write the reaction of ${\text{HC}}_2{H}_3{O}_2$ with ${\text{CaCO}}_3$ .

4. Time to collect 20 mL of gas using 0.5 M $H_2{\text{SO}}_4$ _________________________.Write the reaction of $H_2{\text{SO}}_4$ with ${\text{CaCO}}_3$ .

5. Why does it take different lengths of time to collect 20 mL of gas?

6. Based on the time it took to collect 20 mL of gas, rank the acids in the order of increasing strength.

7. Why did we use 0.5 M $H_2{\text{SO}}_4$ instead of 1.0 M $H_2{\text{SO}}_4$ ?

Part iv. chemical reactions

8. Write the chemical reaction for calcium hydroxide with your exhaled breath.

9. Write your observations for the reaction that took place (i.e. appearance, conductivity, etc.)

10. When in separate solutions, aqueous ammonia, ${\text{NH}}_3$ (aq) and acetic acid ${\text{HC}}_2{H}_3{O}_2$ conduct electricity equally well. However, when the two solutions are mixed a substantial increase in electrical conductivity is observed. Explain.

11. Separately, ammonium sulfate and barium hydroxide solutions are very good conductors. When the two solutions are mixed a substantial decrease in conductivity is observed. Rationalize this.