CHEM 1AL Lecture Notes - Lecture 6: Buffer Solution, Ph Meter, Stopcock

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fuchsiaporcupine53

26 Mar 2016

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Week 2: determination of unknown acid: obtain ph meter and labquest2 from isf (221 latimer) make sure to bring your id. With the help of the gsi make sure your ph meter is set up properly and the reading on the display is correct. In a clean, dry beaker obtain about 65 ml of 0. 1m naoh from the hood. Be sure to record the actual concentration on the label: set up a 25 ml buret on a ring stand with enough clearance below for a 50 ml flask. It is not important the top of liquid is at the 0 ml mark: place the waste beaker under the buret and run about 1 ml of the solution through the buret. Ensure there are no bubbles in the pipet tip. Record the starting mark to the nearest 0. 01 ml. In a separate clean, dry beaker (150-250ml), accurately weigh out up to 0. 25 g of your unknown acid (record the mass).

Related Questions

If you were to over-titrate your calcium solutions in Part B of this lab:a.Would the calculated molarity of EDTA be too high or too low? Explain.

b.Would the calculated molarity of calcium unknown in part C be too high or too low? Explain.

Part B Setup: Complete the following steps, after reading page 6 on how to use volumetric glassware:1.You should have already used a 500 mLvolumetric flaskto prepare an approximately 0.010 M solution of Na2EDTA (Part 1).2.Clean the buret carefully and rinse it two or three times with small amounts (~5mL) of your EDTA solution. Hint; use a clean, dry, labeled beaker to pour solution into the buret. Make sure you rinse through the tip and that no air bubbles are in the tip. Mount the buret on a ring stand using buret clamps. Fill the buret with your EDTA solution nearly to the top mark (to somewhere between the 0 and 5 mL marks for every trialâDO NOT waste time filling the buret to exactly 0.00 mL!). The EDTA is the titrant,the solution added during the titration. Chemistry 161 Lab5Bozlee -Based on S. Critchlow Winter 2018page 4of 11Green River Community College Standardization of the EDTA solution:4.Record the exact reading of the liquid level (bottom of the meniscus) in the buret, recording to the nearest 0.01 mL. This is your initial volume. Note:The burets can be read to a precision of at least +/-0.02 mL. Be sure that all of your readings are precise and consistent.Check with your instructor if you are unclear whether your buret readings are correct.5.In a clean dry beaker, take about 50 mL of standard 0.01000 MCa2+solution; do not take more than this at a time. This is enough to do two trials; if only doing one trial take no more than 30 mL. After proper rinsing, pipet 20.00 mLof this standard Ca2+solution into a 125 mL Erlenmeyer flask. The volumetric pipet tip should NOT be âblown out.â Add about 25 mL of deionized water to the flask.The volume of water is not critical.6.Add a few drops (~6) of indicatorand one full dropperfulof the buffer solutionto the solution in the Erlenmeyer flask.7.Place the stir bar in the flask, place the flask on the stir plate, and set the control for gentle stirring. Or, if you have a good swirling technique with the Erlenmeyer flask, the stir bar and plate is unnecessary. It is essential that the solutions be continually stirred or swirled while titrating.8.What net volume of titrant should be required for the standard trials? You should be able to predict this by calculation!Slowly add your EDTA solution from the buret until the endpoint is reached. The endpointin this titration is the point at which the solution in the Erlenmeyer flask first turns a distinct blue. The color change of the indicatorat the endpoint signals that the equivalence pointhas been reached, where the reactants are in the correct stoichiometric ratio to completely react. As you near the endpoint, add EDTA drop by drop to avoid âovershooting the endpoint.â Record to the nearest 0.01 mL the exact liquid level of EDTA in the buret (your final volume), and calculate the net volume of EDTA used in the titration by subtracting the initial volume from the final volume of EDTA.9.Discard your waste in the appropriate container, using only a very small amount of DI water as the first rinse. Then rinse out your Erlenmeyer flask thoroughlywith several portions of DI water at your sink. Refill the buret (always to between 0 and 5 mL) if you will do another trial. 10.Repeat steps 4-9 two more times, using a fresh aliquot(measured sample) of standard Ca+2solutioneach time. Ideally your replicate titrations should agree within 0.2 mL

I did the calculation part of it ( bottom right heading calculation ) but I was told they are wrong. Can someone please help me with the calculation paper of this report? The result of the reaction is given.

PART PREPARING STANDARD CSH o SOLUTION g the rare feature on the balance, tare the weighr of the weighing paper to zero. Add enough mass of CoHsoo chal between 0.025-0.035 g Record this exact mass. Transfer the CeH.Coe to a 100 mL volumetric flask. 2, Use a stream of deionized water from a wash boetle to rinse clinging to the inside neck of the Aask. 3. Fill the flask abour half full with de ized water, swirl the flask until all of the solid dissolves. 4. Add enough deionized water to till the flask to rhe calibration mark. Seal the mouth of the flask with Parafilm. 5. Invert the flask several times to mix. This is your standard CsHsoo solution. Making a Solution 2. Using a wal bottle, rinse Add known a the neck or the Mask with into a clea led 3, Fil flask with distilled water and swirl to mix. dow swirlingl the flask and invert several imes to mix, 4, the solution until the men scus is level with etched ine neck of the flask. PART STANDARDIZING THE DCP SOLUTION Transfer exactly 10.00 ml. of C6Haoo standard solution to a clean 250 mL Erlenmeye zed water and 10 mL of pH 3 buffer to the Bask-swirl Add 20 mL of dei Fill the se tbe buret with some of the DCP salution and n set up buret with the DCP (titrant) and then eliminate any bubbles in the rip of the buret.Drain some of the solution out.Record the initial buret reading, 8. Titrate the CEHaoestandard solution with the DCP to the end point. Pink color that stays for 30 seconds Record the final buret reading, Refill the buret. solutions as in step 6. Titrate each solution to the end poinr. Record your 9. Prepare two more nitial and final buret readings for each ritration. 10. Pour all solutions down the drain with lots of running water. Rinse out the 250 ml Erlenmeyer TITRATING THE FRUIT JUICE PART 11. obtain about 20 mL of the frui juice analyte) in a beaker 12. Transfer exactly a 5.00 mLaliquot of the juice to a clean 250 mm. Erlenmeyer Aask. Add 10 mL of 3% (HPO o the Mask. Swirl to mi 13. Titrate the fruit juice with the DCP to the end point. Record the initial and final buret readings. Refill the buret. 14. prepare two more solutions as in step 12. Tittate each so ion to the end point. Record your initial and hnal buret reading ing water. Drain out all the remaining tirrant. utions down the drain with 15, Pour all through the tip Rinse out buret with water, allowing water to d CALCULATIONS Calculate the molarity of your standard CeHao6 solution. of the DCP lculate the molarity Standardizing the DCP Solution ach titration in Part Calculate the average DCP molarity. For each titration in Part III (Titrating the Fruit Juice), calculate the mg of vitamin C (CoHeo6 present. Calculate the average mg of Vitamin C present. Determine how many mLof uice are needed to meet the adult DRI of Vitamin C

Hello I need help with the calculations for my data on my Gas Laws Lab report.

My data	Trial 1	Trial 2	Trial 3	Trial 4
Mass Mg (g)	.034	.044	.043
Volume H2 (mL)	35.5	43.5	42.5
Temperature (Â°C)	20	20	20
Atmospheric pressure (mmHg)	29.8	29.8	29.8
Height difference (mmH2O)	20 cm	12.5 cm	15cm

Calculations:

Moles Mg used

Theoretical moles

H2 produced

Vapor pressure of water (mmHg)

Pressure from height diff (mm Hg)

Pressure of H2 (mm Hg)

Pressure of H2 (atm)

Actual moles H2 produced

Percent yield of H2

Experimental R value (LÂ·atm/molÂ·K)

I think once I see how to do the calculations for trial 1 I can do the rest for the other 2 trials.

Below is the procedure for the lab and the calculations if needed.

PROCEDURE: Obtain a 50 ml gas buret, a â00â rubber stopper and a 600 ml beaker. Your instructor will demonstrate the set-up of the equipment. Place approximately 450 ml of distilled water in your 600 ml beaker. Obtain a 2 inch piece of magnesium metal. Record the mass of the magnesium metal. The mass should not exceed 0.050 g. Wrap the magnesium metal with string so that it will hang down in the gas buret. Place the gas buret in a buret holder on a ring stand. Add 8-10 ml of 6 M HCl to the gas buret. Using your wash bottle carefully add distilled water down the side of the buret, being careful not to disturb the hydrochloric acid you just placed in the buret. If done properly, the distilled water will remain âon top ofâ the hydrochloric acid and not mix with it. Continue adding water until the buret is completely filled. Carefully place the magnesium metal so that it hangs several cm down into the gas buret (holding onto the string). Gently insert the stopper into the buret so that the stopper holds the string in place. Check to be sure that an air bubble has not formed at the stopper. If an air bubble is present, remove the stopper, add more distilled water and re-insert the stopper. Using your distilled water bottle, fill the holes of the stopper with distilled water. Place your finger over the stopper holes and invert the gas buret into the beaker so that the top of the buret is below the water level in the beaker. Clamp the buret in place and allow the reaction to proceed. The more dense hydrochloric acid solution will diffuse downward and react with the magnesium metal to produce hydrogen gas. What do you observe suggesting that a reaction is occurring? Your instructor will write the atmospheric pressure on the board for the day. When the reaction is completed, record the distance between the water in the beaker and the solution in the buret (see figure 1, Pht diff). Without moving the buret, read the volume to the nearest Â± 0.02 ml on the buret. This is the volume of the hydrogen gas. Take the temperature of the solution in the beaker. The temperature of the solution is equal to the temperature of the gas. Stir the solution in the beaker. Wait one minute and record the temperature again. If the temperature is not the same, repeat the process until it remains unchanged. Record the temperature to the nearest Â± 0.1 Â°C. Rinse out your glassware and the buret and repeat the analysis two more times, recording the exact mass of magnesium for each trial. If the data appears suspect for any reason, a fourth trial must be done. Enter your raw data into the lab computer before you leave.

CALCULATIONS: We will look at the data in two different ways: 1. Use the ideal gas law to calculate the actual yield of hydrogen gas and compare it to the theoretical yield based on the moles of magnesium used. 2. Alternatively, using the reasonable assumption for this particular reaction that the yield of hydrogen gas is essentially 100%, the value of R can be determined experimentally from the ideal gas law. You cannot use the theoretical value of R to solve for the experimental R value. The stoichiometrically calculated value for moles of H2 must be used in this instance.

CHEM 1AL Lecture Notes - Lecture 6: Buffer Solution, Ph Meter, Stopcock

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