chem lab final

What mass of solid NaOH would be needed to make 645ml of Freddy's NaOh solution? NaOH = 40 18.46 / 1000 = 0.01846 645 / 1000 = 0.645

0.005514 * 40 = 0.2206 0.2206 / 0.01846 = 11.95 11.95 * 0.645 = 7.71g

if it doesn't dissolved completely

saturated

Convert 45.90cm into meters.

(45.90cm) / 1m /100cm = 0.4590m

A student weighted out 1.106g of KHP How many moles was that? KHP = 204.2

1.106 (1 / 204.2) = 0.005416mol

A solution of KCl is saturated at 50C. O C = 27.6 10 C = 31.0 20 C = 34.0 30 C = 37.0 40 C = 40.0 50 C = 42.6 60 C = 45.5 70 C = 48.3 80 C = 51.1 90 C = 54.0 100 C = 55.6 A. How many grams of solute are dissolved in 100g of water? 42.6gKcl B. What is the total mass of the solution

100g + 42.6g = 142.6g KCl

A titration required 18.38ml of 0.1574 M NaOH solution. How many moles of NaOh were in this volume?

18.38 * 0.1574 / 1000 = 0.002893mol

A student heated a hydrated salt sample with an initial mass of 4.8702s. After the first heating, the mass had decreased to 3.0662g. A. if the sample was heated to constant weight after reheating, what is the minimum mass that the sample can have after the second weighing? Show how you determined your answer

3.0662g - 0.05g = 3.0162

A graduated cylinder contains 20.6ml of water. After a piece of metal is placed into the graduated cylinder, the volume is 23.7ml. The mass of the metal is 34.17g. What is the density of the metal? density = mass/volume

34.17g / 23.7ml - 20.6ml 23.7 - 20.6 = 3.1 34.17 / 3.1 = 11g/ml

A saturated solution of barium chloride at 30C contains 150g water. How much additional barium chloride can be dissolved by heating this solution to 60C?

38.2g (150 / 100) = 57.3g 46.6 (150 /100) = 69.9g 69.9 - 57.3 = 12.6gBrCl

A solution of KCl is saturated at 50C. O C = 27.6 10 C = 31.0 20 C = 34.0 30 C = 37.0 40 C = 40.0 50 C = 42.6 60 C = 45.5 70 C = 48.3 80 C = 51.1 90 C = 54.0 100 C = 55.6 A. How many grams of solute are dissolved in 100g of water?

42.6g KCl

The formation of what three classes of substances caused double displacement reactions to occur in this experiment?

A. Gas B. Precipitate C. Slightly ionized compound, usually water

Aluminum oxide

Al2O3

Since the amount of salt, the volume of water, and the temperature of the systems were identical in both test tubes, how do you explain the difference in time for dissolving the fine vs, the coarse salt crystals?

Coarse salt are bigger than fine so it takes longer for it to dissolve.

CuBr2

Copper (II) Bromide

Arrange Mg, H, Ag in order of their activities, listing the most active first.

Mg, H, Ag

Arrange Pb, Mg, and Zn in order of their activities, listing the most active first.

Mg, Zn, Pb

On the basis of the evidence developed in this experiment: A. Would silver react with dilute sulfuric acid? Why or why not?

No, because silver is less active than hydrogen

lead (II) fluoride

PbF2

AgNO3

Silver Nitrate

In experiment 3, we generated oxygen gas from a reaction. What was the purpose of the manganese dioxide (MnO2) in this reaction?

The manganese dioxide was used as a catalyst and helped speed up the decomposition of hydrogen peroxide to produce water and oxygen

Arrange Cu, Ag, and Zn in order of their activities, listing the most active first.

Zn, Cu, Ag

What was the evidence of a chemical reaction when the anhydrous salt samples were treated with the liquid obtained form the hydrate and with water?

a. Change in temperature (heating) steam appeared when water and anhydrous copper(II) sulfate touched. b. Change in color it when from white to blue

what evidence did you see that indicated the liquid obtained form the copper (II) sulfate pentahydrate was water?

a. When applying the obtained liquid to the cobalt chloride paper it turned white so as with the distilled water. b. When applying the droplets of liquid obtained back into the anhydrous copper(II) sulfate it caused the white powder to change back to blue just as the stilled water did.

If it dissolved completely

unsaturated

Use the solubility data in Table 9.1 to answer the following: Show the calculations. A. What is the percentage by mass of NaCl in a saturated solution of sodium chloride at 50C?

(37.0g NaCl / 37.0g NaCl + 100g) * 100 = 27.0%g NaCl

A student weighed a sample of KHP and found it weighed 1.276g. Titration of this KHP required 19.84mL of base (NaOH). Calculate the molarity of the base. KHP = 204.2

1.276g ( 1 / 204.2) = 0.006248mol 19.84 (1 / 1000) = 0.01984 0.006248 / 0.01984 = 0.3149 M

FOrgetful Freddy weighed his KHP sample, but forgot to bring his report sheet along, so he recorded the mass of KHP on a paper towel. During his titration, which required 18.46 mL of base, he spilled some base on his hands. He remembered to wash his hands, but forgot about the data on the towel, and used it to dry his hands. When he went to calculate the molarity of his base, Freddy discovered that he didnt have the mass of his KHP. His kind teacher told him that the base was 0.2987M. Calculate the mass of Freddys KHP sample. Show work. KHP = 204.2

18.46 * 0.2987 / 1000 = 0.005514mol 0.005514 * 204.2 = 1.126g

A solution of KCl is saturated at 50C. O C = 27.6 10 C = 31.0 20 C = 34.0 30 C = 37.0 40 C = 40.0 50 C = 42.6 60 C = 45.5 70 C = 48.3 80 C = 51.1 90 C = 54.0 100 C = 55.6 A. How many grams of solute are dissolved in 100g of water? 42.6gKcl B. What is the total mass of the solution? 142.6gKCl C. What is the mass percent of this solution at 50C? D. If the solution is heated to 100C. how much more KCl can be dissolved in the solution without adding more water? (42.6 / 42.6 + 100) * 100 = 29.9% E. If the solution is saturated at 100C and then cooled to 30C, how many grams of solute will precipitate out?

55.6 - 37 = 18.6g

A solution of KCl is saturated at 50C. O C = 27.6 10 C = 31.0 20 C = 34.0 30 C = 37.0 40 C = 40.0 50 C = 42.6 60 C = 45.5 70 C = 48.3 80 C = 51.1 90 C = 54.0 100 C = 55.6 A. How many grams of solute are dissolved in 100g of water? 42.6gKcl B. What is the total mass of the solution? 142.6gKCl C. What is the mass percent of this solution at 50C? (42.6 / 42.6 + 100) * 100 = 29.9% D. If the solution is heated to 100C. how much more KCl can be dissolved in the solution without adding more water?

55.6 - 42.6 = 13.0g KCl

Calculate the solubility of potassium bromide at 23C. Hint: Assume that the solubility increases by an equal amount for each degree between 20C and 30C.

70.6 - 65.2 / 10 = 0.54 0.54 * 3 + 65.2 = 66.8g KBr

chromium (III) phosphide

ChP

Write the equation for the decomposition of sulfurous acid

H2SO3 ===> H2O + SO2

On the basis of the reactions observed in the six test tubes, explain why the position of hydrogen cannot be fixed exactly with respect to all of the other elements listed in the activity series in question 5.

Hydrogen cannot be fixed exactly with respect to all of the other elements because hydrogen is less active lead and more active then copper. As a result, hydrogen would have a different position dependent on the reaction.

Arrange all five of the metals excluding hydrogen in an activity series, listing the most active first.

Mg, Zn, Pb, Cu, Ag

What additional test(s) would be needed to establish the exact position of hydrogen in the activity series of the elements listed in Question 5?

The additional test needed to establish the exact position of hydrogen in the activity series would be to determine the reactivity series of H in comparison to Mg, Zn, and Ag

In experiment 3, why were the bottles of oxygen stored with the mouth up?

The bottles of oxygen were stored with the mouth up because oxygen is more dense so it will float to the top and also help trap oxygen.

On the basis of the evidence developed in this experiment: B. Would magnesium react with dilute sulfuric acid? why or why not?

Yes, because Manganese is more active than hydrogen thus, it would replace hydrogen..

When the unknown was heated, could the decrease in mass have been partly due to the loss of some substance other than water? Explain.

Yes, it could also decrease in mass due to a decomposition of the heated salt, resulting in a black color change.

HI(aq)

hydroiodic acid

Since the amount of salt, the volume of water, and the texture of the salt crystals were identical in both the test tubes, how do you explain the difference in time for dissolving at the hot vs. cold temperatures?

Hot temperature dissolve salt faster because heat is involve which will speeds up the process.

If you had added 50ml of water to a sample of KHP instead of 30ml, would the titration of that sample then have required more, less, or the same amount of base? Explain

It would required the same amount of base because water content don't change the amount of acid or base that care in the flask

A student heated a hydrated salt sample with an initial mass of 4.8702s. After the first heating, the mass had decreased to 3.0662g. A. if the sample was heated to constant weight after reheating, what is the minimum mass that the sample can have after the second weighing? Show how you determined your answer B. the student determined that the mass lost by the sample was 1.8053. What was the percent water in the original hydrated sample? Show calculation setup.

(1.8053 / 4.8702) * 100 = 37.07%

A solution of KCl is saturated at 50C. O C = 27.6 10 C = 31.0 20 C = 34.0 30 C = 37.0 40 C = 40.0 50 C = 42.6 60 C = 45.5 70 C = 48.3 80 C = 51.1 90 C = 54.0 100 C = 55.6 A. How many grams of solute are dissolved in 100g of water? 42.6gKcl B. What is the total mass of the solution? 142.6gKCl C. What is the mass percent of this solution at 50C?

(42.6 / 42.6 + 100) * 100 = 29.9%

In experiment 3, we saw that when a lit candle was allowed to burn in a bottle of oxygen and then in a bottle of air, the candle burned longer when in the bottle of oxygen. Explain why this occurred.

The candle burned longer in the bottle that contained higher amount of oxygen because oxygen supports combustion so the candle had more oxygen to react with. In comparison, the bottle of air had less oxygen and didn't have as much oxygen needed for combustion, so it burned for a shorter amount of time.