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CHAPTER 4 REGULAR HOMEWORK:

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Order may vary but all questions are available. Use CTRL + F to find all the questions.

Explanation

 

Question 1

When a solution of ammonium carbonate and magnesium chloride are mixed, what precipitate if any is formed?

Select one:
Correct

 

Explanation

(NH4)2(CO3)  + MgCl2   ---> MgCO3   + 2 NH4Cl


One of these things is not like the other...


Hint its a solid 

Another hint its insoluble 

Yet another hint it's to the left

 

Question 2

When a solution of nitric acid and sodium hydroxide are mixed, what precipitate if any is formed?

Select one:
Correct

 

Explanation

Acid + base == salt and water formed

 

Question 3

When a solution of beryllium sulfate and calcium hydroxide are mixed, what precipitate if any is formed?

Select one:
Correct

 

Explanation

Be(SO4)  + Ca(OH)2  ---> CaSO4    + Be(OH)2


According to the solubility rules neither product is soluble making them both solids aka precipitates because the two regents are liquids/aqueous.

 

Question 4

When a solution of sodium sulfide and iron (III) chloride are mixed, what precipitate if any is formed?

Select one:
Correct

 

Explanation

3Na2S + 2FeCl3  --> Fe2S3   + 3NaCl


Fe2S3 is the only insoluble product

 

Question 5

When a solution of ammonium carbonate and lead (II) acetate are mixed, what precipitate if any is formed?

Select one:
Correct

 

Explanation

(NH4)2CO3  + Pb(CH3COO)2  -->  2NH4(CH3COO)  + Pb(CO3) 


only one precipitate.. you guess it its PbCO3

 

Question 6

When a solution of potassium hydroxide and zinc chloride are mixed, what precipitate if any is formed?

Select one:
Correct

 

Explanation

Writing out the formula always helps and is good practice.


2KOH  + ZnCl2  ---->  2 KCl   + Zn(OH)2



KCl is aq meaning aqueous and soluble in this solution whilst Zn(OH)2 is s meaning solid and insoluble in this solution

 

Question 7

Aqueous solutions of cobalt (II) bromide and sodium hydroxide are mixed. Correctly match the following:
CoBr2(aq) + 2NaOH(aq) -->2NaBr(aq) + Co(OH)2(s) Correct
Co2+(aq) + 2Br-(aq) + Na+(aq) + OH-(aq) --> 2Na+(aq) + 2Br-(aq) +Co(OH)2(s) Correct
Co2+(aq) + OH-(aq) -->Co(OH)2(s) Correct
Na+(aq) and Br-(aq) Correct

 

 

Question 8

What mass (in g) of sodium sulfate, Na2SO4, is needed to prepare 380. mL of a 1.20 M solution?

Correct

 

Explanation

3 Sig. Fig.

120 moles Na2SO4/ 1L * 0.380 L  = 0.456 mol Na2SO4

0.456 mol Na2SO4 = Xg/ (142.04 g/mol Na2SO4)

X= 64.77 g Na2SO4

 

Question 9

What is the molarity of the sodium ion in sodium sulfate, Na2SO4, prepared by dissolving 6.28 g of sodium sulfate in enough water to form 1.50 L of solution?

Correct

 

Explanation

62.8 g Na2SO4/ (142.04 g/mol) = 0.04421 mol Na2SO4

0.04421 mol Na2SO4/ 1.50 L = 0.029475 M Na2SO4

2(0.029475) = 0.05895 M Na+

 

Question 10

What is the molarity of the carbonate ion in sodium carbonate, Na2CO3, prepared by dissolving 6.6 g of sodium carbonate in enough water to form 0.200 L of solution?

Correct

 

Explanation

6.6 g Na2CO3/ (105.99 g/mol) = 0.06227 mol Na2CO3

0.06227 mol NaCO3/ 0.200 L = 0.31135 M Na2CO3

0.31134 M CO3(2-)  [1:1 ratio]

 

Question 11

Potassium permanganate (KMnO4) solutions are used for the determination of iron in samples of unknown concentration. As a laboratory assistant, you are supposed to prepare 1200. mL of a 0.300 M KMnO4 solution. What mass of KMnO4, in grams, do you need?
Correct

 

Explanation

 

Question 12

What is the molar concentration of a solution of sulfuric acid, H2SO4, if 3.52 mL react completely with 0.973 g of NaOH which was dissolved in 200 mL of water?
Hint given in feedback

Correct

 

Explanation

Hint--to get the right answer you first need to write the balanced neutralization equation.


0.973 g NaOH/ 39.997 g/mol NaOh= 0.224343 mol /2 L = 0.0122M

0.0122 M / 0.00352 L = 3.46 mol

 

Question 13

Pre question hint: Sodium hydroxide is combined with magnesium chloride. What kind of reaction is this and what solid forms? (Check those statements which are true.)

Select one or more:
Correct
Correct

 

Explanation

If it was a combustion reaction carbon dioxide and oxygen would be involved and they are not and it is not a neutralization reaction as an acid and a base haven't reacted to create a salt and water.

 

Question 14

56.0 mL of 4.00 M sodium hydroxide is combined with 41.0 mL of 1.50 M magnesium chloride. What mass in grams of solid forms? (Hint: the total or overall reaction is most useful in doing calculations.)

Correct


 

Explanation

Hint, this is a limiting reactant problem. To get the correct answer the overall balanced equation is needed.


2 NaOH  + MgCl2  --> NaCl + Mg(OH)2

0.056 L *4M = 0.224 mol NaOH

0.041 L * 1.50 M = 0.00615 mol MgCl2


0.0615 mol MgCl2 * 2 mol NaOH/ 1 mol MgCl2 = 0.123 mol NaOh


0.224 mol > 0.123 mol


MgCl2 = limiting reagent


0.0615 mol Mg(OH)2 is made 1:1 ration with MgCl2


0.0615 mol Mg(OH)2 * 58.32 g/mol Mg(OH)2 = 3.586 g Mg(OH)2


 

Question 15

What is the molarity of a solution of calcium hydroxide, Ca(OH)2, if 138 mL is neutralized with 44.86 mL of a 0.403 M HCl?
Hint given in feedback

Correct

 

Explanation

 

Question 16

Potassium acid phthalate, KHC8H4O4, is a crystalline solid that is available in a state of high purity, making it an excellent choice as a standard acid. What is the concentration of a NaOH solution, if it takes 26.00 mL to neutralize a 0.0206 g sample of the acid?

For the neutralization reaction, KHC8H4O4(aq) --> K+(aq) + H+(aq) + C8H4O42-(aq)
Hint regarding acid is given in feedback

Correct

 

Explanation

Note, there is 1 mole H+ for each mole of acid.

KHC8H4O4  ---> K+   +   H+   + C8H4O4  2-


0.206 g acid / ( 204.22 g/mol acid) = 0.00010087 mol

1:1 ratio


0.00010087 mol / 0.026 L = 0.003879 M

 

Question 17

Warm-up for for the next question. What reaction takes place in question 18?

Select one:
Correct

 

Explanation

A solid/ precipitate is formed from two liquids making the reaction a precipitate reaction.


And the solid that is formed is AgCl and is not shown in the net ionic equation as it is soluble.

 

Question 18

A solution is prepared by placing 10.9 g of KCl in a 0.800 L volumetric flask and adding water to dissolve the solid, then filling the flask to the mark. What is the molarity of an AgNO3 solution if 29.1 mL of the KCl solution react exactly with 34.0 mL of the AgNO3 solution?
Hint given in feedback

Correct

 

Explanation

Hint, first find the molarity of the KCl, then use the balanced equation to find the molarity of the silver nitrate.


10.9 g KCl / (74.55 g/mol KCl) = 0.1462 mol KCl / 0.8 L = 0.1822763 M

0.182763 M * 0.0291 L += 0.005318 moles = 0.034 * X M 
0.156 M

1:1 ratio

KCl  + AgNO3 --> KNO3 + AgCl 

 

Question 19

Sodium thiosulfate, Na2S2O3, is used as a fixer in photographic film developing. The amount of Na2S2O3 in a solution can be determined by a titration with iodine, I2, according to the equation: 2Na2S2O3(aq) + I2(aq) --> Na2S4O6 +2NaI(aq).

Calculate the concentration of the Na2S2O3 solution if 28.70 mL of a 0.2210 M I2 solution react exactly with a 100.0 mL sample of the Na2S2O3solution. Use 4 sig. fig.

Aside, the end of the titration is determined by the color. NaI is a pale yellow and I2 is a deep purple. Just when the purple color persists, all the iodine that can react has reacted.

Correct

 

Explanation

4 Sig. Fig.

0.2210 M I2 * 0.287 L = 0.0063427 moles I2
2:1 ratio
0.0063427(2)= 0.0126854 = .100 L * X M
M= 0.12685

 

Question 20

A 0.3120 g sample of a compound made up of aluminum and chlorine is dissolved in 150 mL H2O. When excess AgNO3 is added, 1.006 g of AgCl is precipitated. What is the number of moles Cl in the aluminum chloride sample?

Correct

 

Explanation

AlCl3 + 3 AgNO3 --> 3 AgCl + Al(NO3)3


1.006 g AgCl/ (143.32 g/mol ) = 0.00701926 mol


3:1 AlCl3


0.0071926 mol Cl

0.002339753 mol Al

 

Question 21

What is the number moles of aluminum in the sample.

Correct

 

Question 23

    

AlCl3 + 3 AgNO3 --> 3 AgCl + Al(NO3)3


1.006 g AgCl/ (143.32 g/mol ) = 0.00701926 mol


3:1 AlCl3


0.002339753 mol Al

 

Question 22

How many chlorine atoms are in the empirical Formula of the aluminum chloride compound? For example, MgCl2 has two atoms of Cl for each atom of Mg. You could also say the same thing with moles.

Correct

 

Explanation

  

Question 26

Question 23

 

What is the oxidation state of P in PO4 3-   


Correct

 

Explanation

O: -2

Overall charge: 3-
P + 4(-2)= -3

P : +5

Question 24

 

What is the oxidation state of P in PF5?

 

Correct

 

Explanation

Florine is in Group 7A oxidation charge: -1

So P + 5(-1)= 0

 P = +5

Question 25

 

What is the oxidation state of Cl in HClO4?

 

Correct

 

Explanation

H: +1

O: -2

+1 + Cl + 4(-2) = 0

        Cl= +7

Question 26

 

What is the oxidation state of P in PO4 3-   


Correct

 

Explanation

O: -2

Overall charge: 3-
P + 4(-2)= -3

P : +5

Question 27

 

What is the oxidation state of O in OF?

Correct

 

Explanation

F: -1

O + 2*(-1)= 0

O = +2

Question 28

 

What is the oxidation state of oxygen in KO2?
Select one:
 Correct

 

Explanation

K : +1

+1 + 2(Oxygen)= 0

Oxygen: -.5

Question 29

 

What is the oxidation state of xenon in XeO2F2?
Select one:
 Correct

 

Explanation

O : -2

F: -1

Overall charge of molecule: 0

Xe + (2 x -2)+(2 x -1) = 0

Xe = 6