AP Chemistry : Solutions and States of Matter

年代tudy concepts, example questions & explanations for AP Chemistry

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Example Questions

Example Question #5 :Precipitates And Calculations

A chemist has 5.2L of a 0.3MLi_3 PO_4solution. If the solvent were boiled off, what would be the mass of the remaining solid?

Possible Answers:

Correct answer:

Explanation:

First we will figure out the number of moles ofLi_3 PO_4that we have. We have 5.2 L of a 0.3 M solution, so:

0.3\hspace{1mm} \frac{mol}{L} \times 5.2\hspace{1 mm} L = 1.56 \hspace{1 mm}moles

Now the problem is to find the mass of 1.56 moles ofLi_3 PO_4. First, we need to know the molecular weight ofLi_3 PO_4. We will go to the periodic table and add up the mass of each element present.

(3\hspace{1 mm}\times6.94\hspace{1 mm}\frac{grams\hspace{1 mm} Li}{mol\hspace{1 mm}Li})+30.97\hspace{1 mm}\frac{grams\hspace{1 mm}P}{mol\hspace{1 mm}P}+(4\hspace{1 mm}\times 16\hspace{1 mm}\frac{grams\hspace{1 mm}O}{mol\hspace{1mm}O})= 115.79\hspace{1mm}\frac{grams\hspace{1 mm} Li_3 PO_4}{mol\hspace{1 mm}Li_3 PO_4}

Now the problem is simple as we have the molar mass and the number of desired moles.

115.79\hspace{1 mm}\frac{grams\hspace{1 mm}Li_3 PO_4}{mol\hspace{1 mm}Li_3 PO_4}\times1.56\hspace{1 mm}moles\hspace{1 mm}Li_3 PO_4 = 181\hspace{1 mm}grams\hspace{1 mm}Li_3 PO_4

Example Question #31 :年代olutions

Given a pKaof 6.37 for the first deprotonation of carbonic acid (), what is the ratio of bicarbonate () to carbonic acid () at pH 5.60?

Assume that the effect of the deprotonation of bicarbonate is negligible in your calculations.

Possible Answers:

Correct answer:

Explanation:

Use the Henderson-Hasselbalch equation to determine the ratio of bicarbonate to carbonic acid in solution:

年代olve for the ratio we need to answer the question:

Example Question #7 :Precipitates And Calculations

Theof(at 298K) is. What is the molar solubility of the hydroxide ion () in a saturated solution of?

Possible Answers:

Correct answer:

Explanation:

The dissociation of calcium hydroxide in aqueous solution is:

Theof calcium hydroxide is related to the dissolved concentrations of its counterions:

andare produced in a molar ratio of 1:2; for each molecule of calcium hydroxide that dissolves:

Given avalue of, the molar solubilities of each counterion may be determined by setting. It follows that:

Now, we can use basic algebra to solve for:

年代ince we set, and, multiplying the value ofby two gives the correct answer, which is 0.022M.

Example Question #1 :Precipitates And Calculations

What type of reaction is also known as a precipitation reaction?

Possible Answers:

Double replacement

Combustion

Decomposition

Combination

年代ingle replacement

Correct answer:

Double replacement

Explanation:

可以进一步目前双置换反应rized as precipitation reactions since it is possible to make a precipitate (solid) from mixing two liquids. Combustion reactions involve using oxygen to burn another species, and the products are carbon dioxide and water. Combination reactions involve the synthesis of one molecule from two separate ones; decomposition is the opposite.

Example Question #1 :年代olubility And Equilibrium

Calculate the molar solubility of AgBr in 0.050 M AgNO3at room temperature. The Kspof AgBr is 5.4 x 10-13.

Possible Answers:

1.57 x 10-12M

2.16 M

1.08 M

1.08 x 10-11M

2.16 x 10-11M

Correct answer:

1.08 x 10-11M

Explanation:

Example Question #2 :年代olubility And Equilibrium

Would the molar solubility of Cr(OH)3increase or decrease as the pH is lowered (i.e. made more acidic)?

Possible Answers:

Can not be determined

Increase

There is no change

Decrease

Correct answer:

Increase

Explanation:

年代ince Cr(OH)3is a basic salt, decreasing the pH makes it more soluble.

Example Question #2 :年代olubility And Equilibrium

Calculate the molar solubility of SrF2in 0.023M NaF. The Kspfor SrF2is 4.3 x 10-9.

Possible Answers:

5.2 x 10-4M

3.2 x 10-3M

1.6 x 10-3M

8.1 x 10-6M

3.2 x 10-5M

Correct answer:

8.1 x 10-6M

Explanation:

Example Question #81 :年代olutions And States Of Matter

Calculate the molar solubility of Mn(OH)2at pH 9.5. The Kspfor Mn(OH)2is 1.6 x 10-13.

Possible Answers:

3.5 x 10-4M

1.6 x 10-4M

1.5 x 10-3M

2.4 x 10-3M

2.1 x 10-5M

Correct answer:

1.6 x 10-4M

Explanation:

Example Question #82 :年代olutions And States Of Matter

计算摩尔CaF的溶解度2(Ksp= 3.9 x 10-11) in a room temperature solution of 0.010 M Ca(C2H3O2)2.

Possible Answers:

3.1 x 10-5M

1.6 x 10-2M

3.2 x 10-2M

4.2 x 10-4M

3.7 x 10-4M

Correct answer:

3.1 x 10-5M

Explanation:

Example Question #1 :Other Solution Concepts

A solution on NaCl has a denisty of 1.075 g/mL. If there are 0.475 L of solution present, what is the mass?

Possible Answers:
2.2 g
510.6 g
0.510 g
2.263 g
441.9 g
Correct answer:510.6 g
Explanation:

1.075 g /mL* 0.475L

First, convert to mL

1.075 g /mL*475 mL= 510.6 g

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