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13 Dec 2019

Postlab Help- these are all the questions I need to answer (data at bottom). This was a titration lab where a saturated solution of borax was prepared by adding 25.0 g of borax to 50 mL of distilled water. We used two different temperatures by using a hot plate to heat the solution. After the solid settled, we took 5.0 mL of the decant on top and put it into a graduated cylinder. After this we titrated it with 100 mL of HCl:

Analysis

A1. Determine the concentration of the dissolved B₄O₅(OH)₄^2â in each sample titrated; show a complete calculation for beaker #1.

A2. Calculate K_sp for each borax solution.

A3. Prepare a graph of your results, plotting the two quantities x and y (as defined in the introduction). Label everything clearly! Draw a best fitted line.

A4. Using y=mx+b of your best fitted line, calculate DHÂ° and DSÂ° for this reaction. Make sure to keep track of units, especially for R, so that the units of DHÂ° and DSÂ° work out sensibly.

Post Lab Questions:

Q1) What would happen to experimental Ksp if the buret was contaminated with other acids?

Summary :

Solubility of borax (make sure to indicate the unit and condition) :

Ksp (one or many? What makes sense?) :

Include graph (site the page). Include all relevant information directly on the graph.

Experimental DHÂ° in kJ/mol :

Theoretical DHÂ° in kJ/mol :

Experimental DSÂ° in J/mol K :

Theoretical DSÂ° in J/mol K :

Trial Initial Volume (mL) Change in Volume (mL) Final Volume (mL) Temperature (^oC) Volume decant (mL)

1 0.3 10.6 10.9 24.0 5.0

2 10.9 15.9 26.8 30.5 5.0

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Calculations First Trial UPDATED

Theoretical yield (CaCO3):

Actual yield (CaCO3):

Percent yield:

Moles of Ca present in original solution, based on actual yield:

Mass of CaCl2 present in original solution, based on actual yield:

Can someone please help me with these three easy questions please? Thank you! SHOW ALL WORK!!

THIS IS MY DATA FROM MY LAB EXPERIMENT. I JUST NEED FOR YOU TO FIND THE ANSWERS TO THE ABOVE QUESTIONS WITH WORK SHOWN!

Table 1: Data and Observations
	Mass
CaCl₂ :	ORGINAL MASS: 2.0g AFTER 24 HOURS 5.8g
K₂CO₃ :	2.5g
Filter Paper	2.1 g
Watch Glass	33.6g
Precipitate	3.3g

Procedure

Put on your safety glasses and gloves (provided in your safety box).

Turn on the scale by pressing the button labeled "0/T". If your scale does not turn on, you may have to remove the battery cover and remove a small strip of plastic from the battery housing. Once the scale is on, press the "0/T" button a second time to zero the scale. Make sure that the units are in grams (g). If not, press the M button until the units displayed are in grams.

Place a weigh boat on the scale and record the mass in Table 2. Zero the mass of the weigh boat by pressing the "0/T" button. Your scale should now read 0 g.

Add 2.0 g of CaCl₂ to the weigh boat. Record the mass in Table 2. Set this sample aside, and let it sit exposed to the air (but otherwise undisturbed) for 24 hours. Complete Steps 3 - 23 while you wait.

Place a 250 mL beaker on the scale and zero it.

Add 2.0 g of CaCl₂ to the beaker. Record the exact mass of the powder in Table 1.

Remove the beaker from the scale. Use a 100 mL graduated cylinder to measure and pour 50 mL of distilled water into the beaker and mix with the stir rod until all the CaCl₂ has dissolved.
Note: This is an exothermic process, so the beaker may become warm.

Place a 50 mL beaker on the scale and zero the scale.

Add 2.5 g of K₂CO₃ to the 50 mL beaker. Record the exact mass of the powder in Table 1.

Remove the beaker from the scale. Use the 100 mL graduated cylinder to measure and pour 25 mL of distilled water into the 50 mL beaker. Mix with the stir rod until all the K₂CO₃ has dissolved.

Rinse the stir rod with water.

Add all of the K₂CO₃ solution to the beaker containing the CaCl₂ solution. It is important that all of the K₂CO₃ is added to the beaker. To ensure this, rinse the 50 mL beaker with up to 5 mL distilled water, and pour the rinse in the CaCl₂ solution.

Using the stopwatch to keep time, stir the solution with the stir rod for four minutes. Then, allow it to sit for 15 minutes. This will allow sufficient time for the chemical reaction to occur.

Rinse the stir rod with water.

Place a piece of filter paper on the scale and record the mass in Table 1.

Place a watch glass on the scale and record the mass in Table 1.

Fold the filter paper in half and in half again so that it resembles a triangle with one arched side.

Pull apart one fold of the filter paper so that three sides of the filter paper remain together, with one side making up the other half of the funnel shape (Figure 5).

Hold the funnel over a sink or any sized container. Place the paper into the funnel and use a pipette to drip 5 mL of distilled water around the edges of the filter paper. This will prevent the filter paper from rising up out of the funnel.

Rest the funnel on top of the Erlenmeyer flask.

After 15 minutes has passed, swirl the beaker and slowly filter the solution (that you created in Step 9) from the 250 mL beaker through the filter paper. Additional distilled water may also be used to transfer any remaining solid into the filtration apparatus.

After all the solution has been filtered, use the pipette to rinse the filter paper with approximately 5 mL of isopropyl alcohol to aid the drying process. Allow the isopropyl alcohol to completely drip through the filter before removing filter paper from the funnel.

Carefully remove the filter paper. Unfold and place it precipitate-side up onto the pre-weighed watch glass. Be sure not to lose any precipitate during this transfer.

Allow the precipitate to dry, undisturbed, for at least 24 hours. Determine the mass of the product recovered by re-weighing the system and subtracting the weight of the filter paper and watch glass. Record your data in Table 1.

Re-weigh the sample of CaCl₂ that was allowed to sit exposed for 24 hours. Subtract the mass of the weigh boat and record the mass and your observations in Table 2.

TABLE 2 IS NOT IMPORTANT IN SOLVING THE QUESTION AS IT JUST ASKS FOR MY OBERVATION OF CaCl₂ AFTER 24 HOURS. ALSO TO FIND THE ACTUAL YIELD, YOU WOULD HAVE TO FIND FIRST THE PERCENT YIELD AND THEORTICAL YIELD.

Seperation lab: Will rate question

Separation lab - will choose best answer

Seperation lab: will choose best answer

Separation of a Mixture Laboratory

In this experiment we will separate the different components of a mixture made up of sand (SiO2) and sodium chloride (NaCl, commonly known as salt). Both of these compounds are solid white crystals, so it is difficult to tell them apart with the naked eye. However, each component exhibits different physical properties that can be used to separate one from the other. There are several physical separation techniques that can be used to determine the percent composition of the original mixture.

Materials & Apparatus:

Sand/salt mixture provided in your Lab Kit

2 - Erlenmeyer Flasks

Scale

Water

Graduated Cylinder

Background:

It is important to know how to separate mixtures because many reactions carried out in the laboratory produce mixtures of different compounds. It is often necessary to separate the components of these mixtures, which can be done using several techniques. We will explore a few of these techniques: sublimation, filtration, evaporation and decantation.

Sublimation is the process of a substance passing from the solid to the gaseous state without first passing through the liquid state. Not all substances possess this characteristic. In fact, most substances to NOT sublime under normal conditions, but must be placed under low pressure and low temperature. Ammonium chloride (NH4Cl) and iodine (I2) are both substances that do sublime under normal conditions.

Filtration is the process used to separate the components of a mixture of solid substances that differ in solubility in a certain solvent. You can separate a mixture of solid substances by adding a liquid to the original mixture in which only some of the components of the mixture will dissolve. The resulting mixture, which contains both the dissolved and undissolved substances, is then poured through a filter paper--a porous paper that allows liquids to pass through while retaining any solids. The liquid that has passed through the filter paper is called the filtrate; the solid on the paper is the residue.

Evaporation can also be used to separate the solvent from the solution. A solution can be slowly heated in an Erlenmeyer flask, and the solute will remain after the solvent has evaporated.

Decantation is the process of separating a liquid from a solid (sediment) by gently pouring the liquid from the solid so as not to disturb the solid.

For this experiment, a practical plan is as follows: First combine the solid mixture of the two compounds, sodium chloride (NaCl) and sand (SiO2), with water. This will dissolve the sodium chloride. The sand will not dissolve into the water. We will "filter" the entire mixture, which allows the water in which the sodium chloride is dissolved to pass through, but not the sand. We will now have separated the sodium chloride and the sand. Then, we must evaporate off the water so that we weigh only the two original solids and not the water we added.

Procedure:

(NOTE: Do NOT dispose of any part of your lab until you are 100% positive you do not need it again. It is good practice to keep all parts of your lab until you are finished.)

Record the letter (A, B, C, or D) of your mixture (on the bag contents label) on the line above Data Table 1 below.

Obtain an Erlenmeyer flask [label it 1] and weigh and record the mass.

Add the entire contents of your unknown mixture bag to the flask and weigh and record the mass of the Erlenmeyer flask and the mixture.

Add 10 mL of water (preferably distilled) to the solid in the Erlenmeyer flask [Erlenmeyer flask 1] and stir gently for 5 minutes.

Weigh a new clean, dry Erlenmeyer flask [Erlenmeyer flask 2].

Decant the liquid from Erlenmeyer flask 1 into Erlenmeyer flask 2. This may work better if you place a utensil against the lip of the pouring flask to encourage a slow steady stream of liquid into the second flask.

Add another 10 mL of water to the solid in Erlenmeyer flask 1, stir for 1-2 minutes, and decant this liquid into the Erlenmeyer flask 2 as before.

Repeat with still another 10 mL of water. This process extracts (dissolves) the soluble sodium chloride from the insoluble sand.

Allow the two flasks to dry. Let them dry until the sand appears dry and freely moves when you shake the Erlenmeyer flask a little and the sodium chloride looks dry.

To speed up the process, you can heat the flasks slowly over a burner set on low on your stove top or in the oven (set at 125-200ËF). I would suggest heating it on top of another pan (NOT nonstick coated) Use a low setting and watch closely as you donât want it to boil over.

Allow the Erlenmeyer flasks to cool to room temperature (if they were heated) and weigh the Erlenmeyer flasks and their contents separately. Record their masses in the appropriate sections of the table.

To ensure that there is no water remaining, heat for another 5-10 minutes oven or 1-2 minutes on the stove. Allow to cool to room temperature and reweigh the Erlenmeyer flask. If it is within 0.3 g of your initial weighing you can stop. If the second weighing is not within 0.3 g of your initial weighing, reheat again, cool, and reweigh. The difference between this mass and the mass of the empty Erlenmeyer flask is the mass of NaCl.

Unknown Mixture Label (A, B, C, or D) ___________

Data Table 1

Measure or calculate and record the following (in grams):
mass of the empty Erlenmeyer flask 1:
mass of the Erlenmeyer flask 1 plus the mixture sample:
mass of the mixture sample:
mass of the Erlenmeyer flask 1 and the remaining contents after drying of sand:
mass of Erlenmeyer flask 1 and dry sand (2nd weighing)
Subtract (a) from (e) to obtain the mass of sand in the sample:
Measure or calculate and record the following (in grams):
mass of an empty Erlenmeyer flask 2:
mass of Erlenmeyer flask 2 and dry NaCl (1st weighing)
mass of Erlenmeyer flask 2 and dry NaCl (2nd weighing)
mass of Erlenmeyer flask 2 and dry NaCl (3rd weighing) if necessary
measured mass of dry NaCl:

Assignment Questions (all work must be shown for all calculations):

Using the results of your lab, complete all the questions below.

Upload one picture that is representative of your experiment with this report to the appropriate D2L Brightspace Assignments folder.

Complete Data Table 1 located in the Procedure. Make sure to include all your work for all the calculations performed.

The amount of sodium chloride in the original mixture may also be determined indirectly by subtracting the SiO2 mass from the initial sample mass. Calculate the expected mass of NaCl using this method.

Calculate the percent difference of NaCl (Note: This is not % Error, but it is a similar calculation. This is an error calculation that checks precision between the results of the two methods from the following equation: (Note: the unit for this calculation is â% differenceâ)

% difference=measured mass-mass by subtractionmass by subtraction x 100

What is the mass percent of each component in your mixture: SiO2, and NaCl? (Note: the units for this calculation are â% SiO2â and â% NaClâ)

mass percent=mass of componenttotal mass of sample x 100

Error Analysis: Was your % difference from Assignment Question 4 within 10%? Why or why not? Did your two mass percentages in Assignment Question 5 add up to 100%? Why or why not? What were your biggest sources of error in this experiment? What would you do differently if you were to repeat this experiment? Explain.

What type of properties (physical or chemical) are we using to separate the mixture in this laboratory. Explain your answer.

A mixture is found to contain 0.69 g SiO2, 1.05 g of cellulose, and 2.17 g of calcium carbonate. What is the mass percentage of SiO2 in this mixture?

Assume you have a mixture of NH4Cl, sand, and salt and access to a regular chemistry laboratory. How would you separate the three?Write out what your procedure would be in numbered steps. Please research the answer to this question and properly cite your source. It is alright to research using the internet. However, Wikipedia, Yahoo Answers, Ask.com, and other non-scientific sources cannot be used.

Chemistry Review Guide

Complete the following questions by using your classmates to answer the questions. You are allowed to walk around the classroom to help each other out and talk about the questions, You may also use your notes to help you check your answer or find answer.

If you dissolve a kool-aid packet into a pitcher of water is it a physical or chemical change? Answer:	List 5 signs of chemical changes. Answer:	If 1 had an object that has a density of 2.52g/ml and placed it into a container of water with a density of 1g/ml would the object sink or float? Answer:
Draw an example of the atoms and molecules of a pure substance and a mixture. Answer:	How can you tell if a liquid is more dense than another liquid? Answer?	List 3 examples of physical change. Answer:

Explain what happens to the mass of an object during a reaction. Answer:	What are the units for: Answer: Graduated Cylinder: ________ Meter Stick: ________ Digital Scale: ________	If you tested your beverage with a piece of litmus paper and it turned red, do you have an acid or a base? Answer:
What is the difference between soluble and insoluble? Answer:	Give an example of a soluble solution and an insoluble solution. Answer:	Explain the difference between chemical changes and physical changes? Answer:
During our lab, we took vinegar and baking soda and combined them in a BEAKER. Why wasn't the mass before the reaction the, same as the mass after? (what happened to the mass?) Answer:	Why type of process do I use to separate a mixture? Physical or Chemical? Answer:	How does the density of a copper penny compare to the density of a brick made out of copper and why? (Read this carefully) Answer: