1 CHAPTER 4 - Aqueous Solutions

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Aqueous Solutions: 2. Calcium chloride is a strong electrolyte and it is I I Strong and Weak Electrolytes used to "salt" streets in the winter to melt ice and 1 I snow. Write a reaction to show how this substance I 1. Write a balanced equation which shows how each breaks apart when it dissolves in water.

of the following salts break apart when placed in water

e. NaOH

3. Commercial cold packs and hot packs are available for treating athletic injuries. Both types contain a pouch of water and a dry chemical. When the pack is struck, the pouch of water breaks, dissolving the chemical, and the solution becomes either hot or cold. Many hot packs use magnesium sulfate, and many cold packs use ammonium nitrate.

Write reactions to show how these strong electrolytes break apart when they dissolve in water.

Solution Concentration: Molarity (M) 5. A solution of ethanol (C2HSOH) in water is prepared by dissolving 75.0 mL of ethanol (density =

4. Calculate the molarity of each of these solutions 0.79 &m3) in enough water to make 250.0 mL of a. A 5.623 g sample of NaHC03 is dissolved in solution. What is the molarity of the ethanol in this

enough water to make 250.0 mL of solution. solution? I* I <loz5 I I c*' , 3 * - 7 5 , o ~ L fbfi, - Write the balanced equation that describes this I ML C A ~ YL.o?$ ouZ5* process.

L

I # 1 1

5 . 6 2 3 rJc /I'03 d

1 b / L /!Cd3 I -Y - X-- SY.o( Nr 6 4 2 ~ O L 6. Calculate the concentration of all ions present in

= . . a 8 each of the following solutions of strong electrolytes.

0 1 2 6 67 4 b k W I 2 1 Write the balanced equation that describes each process.

What is the name of NaHC03 ,%), u,L.- L ~ D T &r6u n!hu

b. A 184.6 mg sample of K2Cr207 is dissolved in enough water to make 500.0 mL of solution.

Write the balanced equation that describes this

a. 0.100 mol of Ca(N03)2 in 1 0010 mL of solution.

c. 5.00 g of NH4C1 in 500.0 mL of solution.

What is the name of K2Cr20r 40-/ci5suw dlchfar d . . I I

c. A 0.1 025 g sample of copper metal is dissolved in 35 mL of concentrated HN03 to form cu2+ ions and then water is added to make a total volume of 200.0 mL. Calculate the molarity of cu2+.

Write the balanced equation that describes this process. ~~p~ lccSo. ( ,

- + + R + Cu + fit a 'Cu

Irro/Gfz 16- (C& 4 7

~ C & C - + fw(coC*jr j b . ~ ( & - I . " , r , ? L 0,1025 li Ca, --- 1

1

7. Which of the following solutions of strong 1 1. Describe how you would prepare 2.00 L of each electrolytes contains the largest number of moles of of the following solutions.

3 a . 0.250 M N ~ O H from solid NaOH

b. 50.0 mL of 0.60 M MgCI2

0, 050s L I. 0.250 M NaOH from 1,.00 M NaOH stock solution. EJIIV, = MzVr

( O . Z S ~ H ) ~ . O ~ ~ ) = / j ,oof i ) VL c. 200.0 mL of 0.40 M NaCl y, = 0.m L L f S&*NL

0 9-j-b t 4 t I / ?YlW%

L j NU/ kt([+ 8. What mass of NaOH is contained in 250.0 mL of a 0.400 M of a sodium hydroxide solution? = 38.8~ koOf

~so,o~L,&,+ -

/mrC J r d l d. 0.100 M KzCr01 fiom 1.75 M K2Cr04 stock solution.

f l \u , = f l z u

(0, N) 2 .O(IL = b 1 7 ~ ~ ) ~2

V2 = 0 , / / g L or / ! ~ D , L

9 If 1 0 . 9 of ~ ~ ~ 0 3 is available, what volume of j r* kt L/ ML r ; ; ; 7 G G q m 0.25 M AgN03 can be prepared? I T .. -. - I 12. A solution is prepared by dissolving 1 0 . 6 ~

/0. 3 AhN4 ammonium sulfate in enough water to make 100.0 mL of stock solution. A 10.00 mL sample of this stock solution is added to 50.00 mL of water. Calculate the concentration of ammonium ions and sulfate ions in the final solution.

10. Calculate the sodium ion concentratiop when 70.0 mL of 3.0 M sodium carbonate is added to - 30.0 mL of 1.0 M sodium bicarbonate.

3 Q 4 ~ ‘ $ 3 3 0.0700~ JW. I c!!

& * (0.8, p y ) / b , O o ~ L {$) 6O1O0,o*.L L I j l lto l kZ((J2

2 __ ---- ---- [ M ~ - o1/363=d = O.( /ZP~&'+

13. A standard solution is prepared for the analysis of fluoxymesterone (C20H29F03). An anabolic steroid. A stock solution is first prepared by dissolving 10.0 mg of fluoxymesterone in enough water to give a total volume of 500.0 mL. A 100.0 pL aliquot (portion) of this solution is diluted to a final volume of 100.0 rnL. Calculate the concentration of the final solution in terms of molarity. --...-. - . - .~-- . .

14. A stock solution containing ~n~~ ions was prepared by dissolving 1.584 g pure manganese metal in nitric acid and diluting to a final volume of 1.000 L. Calculate the concentrations of the stock solution, and then calculate the concentration of solutions A, B and C prepared by dilution as described below. a. Stock Solution

b. Solution A, prepared by taking 50.00 mL of stoc$s~lution and diluting to 1000.0 mL.

c. Solution B, prepared by taking 10.00 mL of solution A and diluting to 250.0 mL.

m,q, = & V L

p;;q d. Solution C, prepared by taking 10.00 mL of solution B and diluting to 500.0 rnL.

Precipitation Reactions 17. For the same set of equations, write the balance

15. On the basis of the general rules of solubility, equation, and the net ionic equation. If no predict which of the following substances are likely to be soluble in water. a. aluminum nitrate b. magne~ium~chloride c. rubidium sulfate d. nickel (11) hydroxide e. lead (11) sulfide - .

f. magnesium hydroxide g. iron (111) phosphate h. zinc chloride i. lead (11) nitrate j. lead (11) sulfate

1. cobalt (111) m. chromium

o. ammonium carbonate

precipitate forms, then write "no reaction". ~

-L 16. When the following solutions are mixed J I d.

together, predict the products, and identifl any -K2S(aU + -Ni(NO3)2 (ad + LKw3 + N i S & precipitate that forms using the symbol (4) for precipitate.

&+ 5-'+ d i t z + ~ i * ~ K & t f is4 a ~ e s o 4 (a@ +~tcl(@ + c lee!, t I( 2 s oy I N . ~ z + s - ~ + FJ; s-/J - I

~13t- I * e.

b. 2 A ~ ( N o ~ ) ~ -$~a(on), - .3&03ga (O &), i -Hg~mo3)2 (aq) + -cuso. (aq)+ N$501 b 4- ' 'dl 1r,:.+adr+v:'-,q2* j H~&F@~

c. cacl2 (aq) + Na~sO4 (aq) + 2 EC, C& soy 6 2iW-

- K q , q f l Z + so, -

f c

19. What mass of Na2Cr04 is required to 18. Write net ionic equations for the reaction, if any, precipitate all of the silver ions fi-om 75.0 mL of a that occurs when aqueous solutions of the following 0.100 M solution of AgN03? are mixed. a. ammonium sulfate and barium nitrate $ ~ o , + Na,Cfo y -4 $2 G ~ $

- -

b. lead (11) nitrate and sodium chloride 1s ;?

4' / e / ~ ~ 6 ~ ~ ' ~ , / . .

-j+J ("J + kc(" W', + LU('3 1-1 N q e t q

?b4' + d C r * ?&L&

c. sodium phosphate and potassium nitrate

flL3fi+ t kdo3 d4Ao3+ I(,PO~

d. sodium bromide and rubidium chloride

20. What volume of 0.100 M Na3P04 is required to precipitate all the lead (11) ions f r o r n ~ 1 5 0 . 0 ~ of 0.250 M Pb(N03)2? nC(

e. copper (11) chloride and sodium hydroxide I . ,

CuCI, + Ah0# -b t @&@L 21. What mass of solid aluminum hydroxide can be produced when 50.0 mL of 0.200 M A1(N03)3 is

Cct2 t 4 ~ h ( ~ l f ) ~ & added to 200.0 mL of 0.100 M KOH?

A( (h4) +\l~04--b >[ (d83$t k% - f. chromium (11) chloride and sodium hydroxide 3

1 A ['J + 3 4 d + 6 A i (~o3) ' ib - j CrCIz + Nn~tf + NLC(+ CC('% I

----D

C r f 2 + ~ d - + ~ r l j ~ l & I,% IAP- I / n . 1 4 1 ~ ~ 3

g. silver nitrate and ammonium carbonate .-

A NO3 + 1 A co,k Nl$N2 5 a.

6 dA( t Poi2+ A ~ ~ c o ~ &

- -- - -

Acid -Base Reactions

22. Write the balanced formula and the net ionic equations for each of the following acid-base reactions.

d. 3 HNO, (,I + A ~ ( O H S ~ (s) + '~16403. + J K O HolY

3 ~ ' f 3& + A I ( Q ~ C ) ~ ~ + nl3+~3& + 3/ / ,0

f. - HC2H302 (a,) + KOH (,I -. I( e, a, 4 + -* H c ~ Y ~ ~ + & t + ~ n - -b &-t~/4'0; + H z a

23. Write the balanced equation and the net ionic equation for the reactions that occur when the following are mixed.

a. potassium hydroxide (aqueous) and nitric acid

b. barium hydroxide (aqueous) and hydrochloric acid t4o !C-

/ # + t Ol- / - -b 14, q c. perchloric acid an8 solid iron (111) hydroxide f-h ff

3 H C / O t F ~ C O ~ ) ~ fi(clOJ * + 3 o ~ - + 31+t 3 6 7 +

/ SO& ----lb / f76 ( d. solid silver hydroxide and hydrobromic acid

e. aqueous strontium hydroxide and hydroiodic acid * .Sr [OH), + wt

8 ,I f. solid chromium (111) hydroxide and nitric acid \ n

25. A 25.0 mL sample of hydrochloric acid solution requires 24.16 ml, of 0.106 M sodium hydroxide for plete neutralization. What is the acid solution? o r q l 6 f l ~ o ~ .JC I

- ., p - c o d - -=hd,d L.

26. What volume of 0.0200 M calcium hydroxide is required to neutralize 35.00 mL of 0.500 M nitric acid? - IwI Hf HW,Ly &- / ~ o / o H - \bIfc(o&), 1~ &(tffk

L I C U ~ I ~ U ~ ~ J M J I I + + ~ C ~ U L ~ - A& oam+/ c.cot$,-

27. A student titrates an unknown amount of potassium hydrogen phthalate (KH6a474, often abbreviated as KHP) with 20.46 mL of a 0.1000 M NaOH solution. KHP (molar mass = 204.22 ghol ) has one acidic -

hydrogen. What mass of KHP was titrated (reacted completely) by the sodium hydroxide solution?

I - K T c + H,d: kj& -e -OK -n <

28. The concentration of a certain sodium hydroxide solution was determined by using the solution to titrate a sample of potassium hydrogen phthalate, KHP (see question 27). In the titration, 34.67 mL of the sodium hydroxide solution was required to react with 0.1082 g KHP. Calculate the molarity of the sodium hydroxide.

&og KdP -A NKP -C I - k o

check: Oxidation-Reduction Reactions (Redox)

29. Assign oxidation states for all atoms in each of the follow$ compounds -ti *"t-aJ V 0. Specify which of the following are oxidation-

a. KMn04 reduction and identify the oxidizing agent (the substance being ozidized) and reducing agent (the

check: substance being reduced).

+ Y - 4 (Remember: LEO says GER) (4

b. Ni02 -LC I

4 a- check: ( 4 y ) ~ 1 + 2 ( -2 )0=0 Is this a redox reaction frl+2 - & +.r + (q - \/ -.- - n p D e T - w - S v *

q6r) (-246 c. Na4Fe(OH)6 reducing agent: oxidizing agent: tip

check: +,I/ -343 &$'-I 4( t )Na + ( +L ) ~ c + 6( -2 )o+ 6( I )H = 0 , b. HCI(,) + NHI (g) + NhC1 (s)

Y f -* - -- 2 + ( -a) 4 0.4 + 1 +i-6 I*

- Is this a redox reaction d. (NI%)2HP04 p3 H + / ;+SOS 1 Y IQ

-%+8+l - '2 - -

2( -3 )N + 9( 4 I )H + ( $ )P+ 4( -L)o = 0 / reducing agent: oxidizing agent: 4 iJ - v

'-6) 2 . e. NO; IN- +3 02 j - 212-2 / i r - 7

c. + 2 Hz0 (1) - 4 HCl(,) + SiO2 (,) check: ( + ~ h + 2 ( - q o = - 1 d

- b Is this a redox reaction -ir,:$? G---- y 10 f. NO3-

check: -9

+';.a,z

g. uoz2+ --

N + Z 0 -2

reducing agent: * V F

oxidizing agent: / ( t T - ) ~ + 3 ( - ~ ) 0 = - 1 f

-le- checki

3-6 - ( )u + 2( - ' )0 = +2 Is this a redox reaction 3 (f7{--2)f

91 h. Cr203

check: 0 J reducing agent: .% oxidizing agent: 5) 2( f 3 ) ~ r + 3 ( -2 )o=

Is this a redox reaction Y I@

reducing agent: oxidizing agent: I.L 32. Classify each of the following half-reactions as

31. Classify each of the following half-reactions as oxidation or reduction. How many electrons are exchanged in each redox process? oxidation or reduction, then balance.

-FVe - * q A +e ..6 R a ) ? ~ i 2 + ( $ 2 Ni203 (s) (basic] I

0 I@ 6 2 (PI +1o2-(aql 3 c.

.*4 e- 0 -3 $ N , - . . - < .p - . . ,

. ..- ____^ . . . . . 'Z "

+ i/+<:;; 5.! .3 ~ ; $ ; ..\ +'! -ti "2 -:/ - .- L.

l_l_---_._-.__ r . . . _ 0;

MpOi ( a d + MdOl- (s) v e- --. m ---- . - T

44 d,+z.+ 6 - -+ N i z 0 3 ~ ~ e - + 3 / l 2 0 4 !2 -,q . . (... ,d

. - .._."-----. /'

j C r ~ 0 7 ~ - ( a d +~!CF~' ( a d "P e- 7 -> ,

6 , [>C3$ ,' r

(acidic) QI R -1 0

Cl-(ad + Cl2 (g) - I e m

- r c ---yG----- - 7 -3

@R b

F - 7 - s NH4+(ad + N2 (g) -3 e- @ R C) Mn2+(ad + MnOc (ad (acidic) - - 7.--I- +2 .? 7

mntz+ ~ 4 % -I 5-e- -Z u -i s +A-r -- - -

._A C _ - - . , t

+ .- - -+p om CZ130H(aa + CH20 (ad d e- Cjh'zo , 2. & 3 + 2 q

___-____ _____.__&.L_L--'-------.'~ -

- I -

To balance half-reactions.. . E '= ' I ' * ' ( l. Balance the atoms of the element b* oxidized or I . ...-------..-. . . h '7. reduced.

2. Balance oxidation number by adding electrons. 3 Balance the charge bv adding H+ ions in acidic

+ 3 ~ solutions: O H ions in basic solution. r2--‘; 4. Blance hydrogen by adding H20 molecules. * -g 5. Check to make sure that oxygen is balanced.

0 @ d) CrO12- (ad + Cr3+ (ad (acidic)

- ze 33. Bal ce the following oxidation-reduction reactions that occur in

a. gS) + HClw +!n2+ is) + Hi + CI-(,) --k--3Q ?

I

--D ~ ~ ' ' f l e / L: -t 2 +C i - - -42 L L , XI? - IC--

, - J l t ' l c ( + - J c - . .

I .-

3n u zfl -1 7 , * s

J d c ( f,*--+ 21, t 2 0 - , -----a F

4 ~ $ t ~ n ' ' ~ d C / '

34. Balance the following oxidation-reduction reactions that occur in basic solution. a. CU(,) + N03-(ad+ cu2+ NO(,)