worked solutions ch. 11

8/12/2019 Worked Solutions Ch. 11

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Worked Solutions

Chapter 11

Question 5

What is the concentration in grams per litre of (a) a 0.1 M HCl solution (b) a 0.05 M Na2CO

solution (c) a 0.05 M NaOH solution (!) a 0.01 M "OH solution (e) a 0.2 M HNOsolution#

Answer:

(a) Molar mass of HCl $ %.5 g mol&1

0.1M HClsolution contains 0.1 moles $ 0.1 X %.5 g in 1 litre

Concentration of HCl solution $ .%5 g l'1

(b) Molar mass of Na2CO$ 10% g mol&1

0.05M Na2CO solution contains 0.05 moles $ 0.05 X 10% g in 1 litre

Concentration of Na2COsolution $ 5. g l'1

(c) Molar mass of NaOH $ 0 g mol &1

0.05M NaOHsolution contains 0.05 moles $ 0.05 X 0 g in 1 litre

Concentration of NaOH solution $ 2 g l'1

(!) Molar mass of "OH $ 5% g mol &1

0.01M "OHsolution contains 0.01 moles $ 0.01 X 5% g in 1 litre

Concentration of "OH solution $ 0.5% g l'1

(e) Molar mass of HNO$ % g mol&1

0.2M HNO solution contains 0.2 moles $ 0.2 X % g in 1 litre

Concentration of HNOsolution $ 12.% g l'1

Question 6

solution contains 25 g of potassium h*!ro+i!e ("OH) in 1 litre of solution. Calculate the

concentration of the solution in moles per litre.

Answer:

25 g "OH $ 25,5% moles "OH $ 0.5 moles "OH

Concentration of the solution $ 0.5 mol l&1($0.5 M)

Question 7

-he concentration of a potassium manganate(//) solution ("MnO) is %.2 g l'1. What is the

concentration of this solution in moles per litre#

Answer:

%.2 g "MnO$ %.2,15 moles "MnO$ 0.0 moles "MnO

Concentration of the solution $ 0.0 mol l&1($ 0.0 M)

1


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Question 8

solution contains g of NaOH in 250 cmof solution. Calculate the concentration of the

solution in moles per litre.

Answer:

g of NaOH in 250 cmof solution is euialent to + 1000,250 $ 1% g in 1 litre

1% g NaOH $ 1%,0 moles NaOH $ 0. moles NaOH

Concentration of the solution $ 0. mol l&1($ 0. M)

Question 9

solution contains .3 g H24Oin 100 cmof solution. Calculate the concentration of the

solution in moles per litre.

Answer:

.3 g of H24Oin 100 cmof solution is euialent to .3 + 1000,100 $ 3 g in 1 litre

3 g H24O$ 3,3 moles H24O$ 0.5 moles H24O


Question 10

bottle of ine contains 3 g of ethanol (C2H5OH) in 600 cmof solution. Calculate the

concentration of ethanol in moles per litre.

Answer:

3 g of C2H5OH in 600 cmof solution is euialent to 3 + 1000,600 $ 60 g in 1 litre

60 g C2H5OH $ 60,% moles C2H5OH $ 1.52 moles C2H5OH


Question 11

What mass of potassium h*!ro+i!e ("OH) is containe! in 500 cmof 0.05 M potassium

h*!ro+i!e solution#

Answer:

17000 cmof 0.05 M "OH solution contains 0.05 moles

500 cmof 0.05 M "OH solution contains 0.05 X 500 , 17000 moles

$ 0.025 moles

Molar mass of "OH $ 5% g mol &1

Mass of "OH containe! in 500 cmsolution $ 5% X 0.025 g

$ 1. g

2


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Question 12

What mass of so!ium h*!ro+i!e (NaOH) is containe! in 250 cmof 0.02 M so!ium

h*!ro+i!e solution#

Answer:

17000 cmof 0.02 M NaOH solution contains 0.02 moles

250 cmof 0.02 M NaOH solution contains 0.02 X 250 , 17000 moles

$ 0.005 moles

Molar mass of NaOH $ 0 g mol &1

Mass of NaOH containe! in 250 cmsolution $ 0 X 0.005 g

$ 0.2 g

Question 13

Ho man* moles of h*!rochloric aci! (HCl) are containe! in 25 cmof 0.05 M h*!rochloric

aci! solution#

Answer:

Number of moles $ olume in cmX concentration inmoles per litre , 17000

$ 25X0.05 17000

$ 0.00125

Question 1!

Ho man* moles of sulfuric aci! (H24O) are containe! in 15 cmof 0.02 M sulfuric aci!

solution#

Answer:


$ 15X 0.02 17000

$ 0.000

Question 15

Ho man* moles of so!ium carbonate are there in 100 cm

of 0.05 M so!ium carbonatesolution#

Answer:


$ 100X 0.05 17000

$ 0.005

Question 16

-he concentration of !issole! o+*gen in a ater sample is 0.00002 M. Calculate the

concentration of !issole! o+*gen in the ater sample in p.p.m.


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Answer:

Molar mass of O2$ 2 g mol&1

-here are 0.00002 moles of !issole! o+*gen in 1 litre of the ater sample.

Mass of O2in 1 litre $ 0.00002x2 g $ 0.000% g $ 0.000%x 17000 mg $ 0.% mg

Concentration of !issole! o+*gen in the ater sample $ 0.% p.p.m.

Question 17

solution contains 25 g so!ium h*!ro+i!e in 1 litre of solution. 8+press the concentration of

the solution in 9 (,).

Answer:

-he solution contains 25 g NaOH in 1 litre.

100 cmof solution contains 25 x 100 , 17000 g NaOH $ 2.5 g NaOH

Concentration of NaOH in the solution $ 2.59 (,)

Question 18

solution contains g so!ium h*!ro+i!e in 500 cmof solution. 8+press the concentration

of the solution in 9 (,).

Answer:

-he solution contains g so!ium h*!ro+i!e in 500 cm

of solution.100 cmof solution contains x 500 , 17000 g NaOH $ 1.% g NaOH

Concentration of NaOH in the solution $ 1.%9 (,)

Question 19

bottle of inegar contains 66 cm ethanoic aci! in 600 cm of solution. 8+press the

concentration of ethanoic aci! in the solution in 9 (,).

Answer:

-he solution contains 66 cm ethanoic aci! in 600 cm of solution.

100 cmof solution contains 66 x 100 , 600 cm ethanooic aci! $ 11 cm ethanoic aci!

Concentration of ethanoic aci! in the solution $ 119 (,)

Question 20

solution contains 20 g potassium h*!ro+i!e in 250 g of solution. 8+press the concentration

of the solution in 9 (,).

Answer:

-he solution contains 20 g "OH in 250 g of solution.

100 g of solution contains 20 x 100 , 250 g "OH $ g "OH


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Concentration of "OH in the solution $ 9 (,)

Question 21

-he label on a bottle of ine in!icates that the concentration of alcohol in the ine is

39 (,). What olume of alcohol is there in 250 cmof the ine#

Answer:

100 cmof the ine contains 3 cmalcohol.

250 cmof the ine contains 3 x 250 , 100 cmalcohol $ 22.5 cmalcohol.

Question 22

What olume of ethanol is there in 500 cmof a 59 solution of ethanol in ater#

Answer:

100 cmof the solution contains 5 cmethanol.

500 cmof the solution contains 5 X500 , 100 cmethanol $ 25 cmethanol.

Question 26

/f 25 cm of a 1 M h*!rochloric aci! solution is !ilute! to a olume of 500 cm ith ater7

hat is the concentration of the !ilute! solution#

Answer:

!ilX M!il$ concX Mconc

500X M!il$ 25 X1

M!il $ 25 X1 , 500 mol l&1 $ 0.05 mol l&1

Concentration of the !ilute! solution $ 0.05 mol l&1

Question 27

/f 10 cm of a 0.1 M potassium h*!ro+i!e solution is !ilute! to a olume of 250 cm ith

ater7 hat is the concentration of the !ilute! solution#

Answer:


250X M!il$ 10 X0.1

M!il $ 10 X0.1 , 250 mol l&1 $ 0.00 mol l&1

Concentration of the !ilute! solution $ 0.00 mol l&1

Question 28

What olumeof a 1 M h*!rochloric aci! solution is nee!e! to ma:e up 500 cm of a 0.1 M

h*!rochloric aci! solution#Answer:

5


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500X 0.1 $ concX1

conc$ 500X 0.1 , 1 mol l&1 $ 50 cm

olumeof 1 M h*!rochloric aci! solution nee!e! $ 50 cm

Question 29

What olumeof a 0.5 M sulfuric aci! solution is nee!e! to ma:e up 250 cm of a 0.1 M

sulfuric aci! solution#

Answer:


250X 0.1 $ concX0.5

conc$ 250X 0.1 , 0.5 mol l&1

$ 50 cm

olumeof 0.5 M sulfuric aci! solution nee!e! $ 50 cm

Question !0

/n a titration7 25 cm of a 0.05 M so!ium carbonate solution reuire! 22 cmof a h*!rochloric

aci! solution for complete neutralisation. Calculate the concentration of the h*!rochloric aci!

solution.

-he euation for the reaction is

2HCl(a); Na2CO(a) 2NaCl(a) ; H2O(l) ; CO2(g)

Answer:

1xM1xn2 $ 2xM2xn1

22xM1x 1$25x 0.05x2

M1$ 25x0.05x 2 , (22x 1)

$ 0.11 mol l&1

Concentration of h*!rochloric aci! solution $ 0.11 mol l&1

Question !1

/n a titration7 25 cm of a so!ium h*!ro+i!e solution reuire! 13.5 cmof a 0.1 M

h*!rochloric aci! solution for complete neutralisation. Calculate the concentration of the

so!ium h*!ro+i!e solution. -he euation for the reaction is

HCl(a); NaOH(a) NaCl(a) ; H2O(l)

Answer:

1xM1xn2 $ 2xM2xn1

13.5x0.1x 1$25x M2x1

M2$ 13.5x0.1x 1 , (25x 1)

%


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$ 0.06 mol l&1

Concentration of so!ium h*!ro+i!e solution $ 0.06 mol l&1

Question !2

/n a titration7 25 cm of a potassium h*!ro+i!e solution reuire! 22.5 cmof a 0.01 M

h*!rochloric aci! solution for complete neutralisation. Calculate the concentration of the

potassium h*!ro+i!e solution. -he euation for the reaction is

HCl(a); "OH(a) "Cl(a) ; H2O(l)

Answer:

1xM1xn2 $ 2xM2xn1

22.5x0.01x 1$25x M2x1

M2$ 22.5x

0.01x

1 , (25x

1) $ 0.003 mol l&1

Concentration of potassium h*!ro+i!e solution $ 0.003 mol l&1

Question !3

/n a titration7 hat olumeof a 0.1 M h*!rochloric aci! is reuire! to neutralise 25 cmof a

0.02 M so!ium carbonate solution# -he euation for the reaction is


Answer:

1xM1xn2 $ 2xM2xn1

1x0.1 x 1$25x 0.02 x2

1$ 25x 0.02 x2 , (0.1x 1)

$ 10 cmof h*!rochloric aci!

Question !!

/n a titration7 hat olumeof a 0.05 M h*!rochloric aci! is reuire! to neutralise 25 cmof a

0.0 M so!ium h*!ro+i!e solution# -he euation for the reaction is


Answer:

1xM1xn2 $ 2xM2xn1

1x0.05 x 1$25x 0.0 x1

1$ 25x 0.0 x1 , (0.05x 1)

$ 20 cmof h*!rochloric aci!

6


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Question !5

What olume of 0.02 M H24O is nee!e! to neutralise 25 cm of a 0.05 M NaOH solution#


H24O(a) ; 2NaOH(a) Na24O(a) ; 2H2O(l)

Answer:

1xM1xn2 $ 2xM2xn1

1x0.02 x 2$25x 0.05 x1

1$ 25x 0.05 x1 , (0.02x 2)

$ 1.25 cmof sulfuric aci!

Question !6/n a titration7 25 cm of a 0.12 M so!ium h*!ro+i!e solution reuire! 2 cmof a sulfuric aci!

solution for complete neutralisation. Calculate (a) the number of moles of so!ium h*!ro+i!e

consume! (b) the number of moles of sulfuric aci! consume! an! (c) the concentration of the

sulfuric aci! solution. -he euation for the reaction is


Answer:

(a) /n the titration7 25 cm of 0.12 M so!ium h*!ro+i!e solution ere use!.

17000 cmof 0.12 M so!ium h*!ro+i!e solution contains 0.12 moles.

25 cmof 0.12 M so!ium h*!ro+i!e solution contains 0.12 X 25 , 17000 moles

$ 0.00 moles

(b) -he euation for the reaction is


2 moles of NaOH react ith 1 mole of H24O

1 mole of NaOH reacts ith 0.5 moles of H24O

0.00 moles of NaOH reacts ith 0.00X 0.5 moles of H24O

$ 0.0015 moles of H24O

(c) /n 2 cmof the H24O solution there are 0.0015 moles of H24O

/n 17000 cmof the H24O solution there are

0.0015X 17000 , 2 moles $ 0.0%25 moles

Concentration of the sulfuric aci! solution $ 0.0%25 mol l&1

Question !7

20 cm

of a 0.125 M HCl solution ere neutralise! b* 25 cm

of a "OH solution. -heeuation for the reaction is


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(a) Ho man* moles of HCl ere consume!#

(b) Ho man* moles of "OH ere neutralise!#

(c) Ho man* moles of "OH ere there in 25 cmof the "OH solution#

(!) Calculate the concentration in mol l&1of the "OH solution.

Answer:

(a) /n the titration7 20 cm of 0.125 M HCl solution ere use!.

17000 cmof 0.125 M HCl solution contains 0.125 moles.

20 cmof 0.125 M HCl solution contains 0.125 X 20 , 17000 moles

$ 0.0025 moles


HCl(a); "OH(a)

"Cl(a) ; H2O(l)One mole of HCl reacts ith one mole of "OH.

0.0025 moles of HCl react ith 0.0025 moles of "OH.

(c) -he 25 cmof "OH consume! containe! 0.0025 moles.

(!) /n 25 cmof the "OHsolution there are 0.0025 moles of "OH

/n 17000 cmof the "OHsolution there are

0.0025X 17000 , 25 moles $ 0.1 moles

Concentration of the "OH solution $ 0.1 mol l&1

Question !8

What mass of magnesium ill react ith 20 cm of a 0.03 M h*!rochloric aci! solution# -he

euation for the reaction is

2HCl(a) ; Mg(s) MgCl2(a) ; H2(g)

Answer:

17000 cmof 0.03 M HCl solution contains 0.03 moles

20 cmof 0.03 M HCl solution contains 0.03 X 20 , 17000 moles

$ 0.001 moles


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What mass of magnesium ill react ith 15 cm of a 0.12 M sulfuric aci! solution# -he


H24O(a) ; Mg(s) Mg4O(a) ; H2(g)

Answer:

17000 cmof 0.12 M H24Osolution contains 0.12 moles

15 cmof 0.12 M H24Osolution contains 0.12 X 15 , 17000 moles

$ 0.001 moles


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Question 51

2.31 g of a monobasic aci!7 H>7 ere !issole! in ater an! ma!e up to 250 cm ith ater.

-his solution as titrate! ith 0.10 M so!ium h*!ro+i!e solution. 25 cm of the so!ium

h*!ro+i!e solution reuire! 22.5 cmof the H> solution for complete neutralisation. -he


H>(a); NaOH(a) Na>(a) ; H2O(l)

(a) Calculate the concentration in (i) g l&1(ii) mol l&1of the aci!.

(b) Calculate the molar mass of H>.

Answer:

(a) (i) 2.31 g of H> in 250 cmis euialent to 2.31 > g $ 11.% g in 1 litre. -hus the

concentration is 11.% g l&1

(ii)

1xM1xn2 $ 2xM2xn1

22.5xM1x 1$25x 0.10x1

M1$ 25x0.10x 1 , (22.5x 1)

$ 0.12 mol l&1

Concentration of H> solution $ 0.12 mol l&1

(b) 0.12 moles has a mass of 11.% g

1 mole has a mass of 11.%,0.12 g $ 36 g

-he molar mass of H> is 36 g mol &1

Question 52

Cr*stals of h*!rate! so!ium carbonate (Na2CO.+H2O) of mass .15 g ere !issole! in

ater an! ma!e up to 250 cmin a olumetric flas:. 25 cm of this solution reuire! 15 cmof

a 0.15 M h*!rochloric aci! solution for complete neutralisation. -he euation for the reaction

is

2HCl(a); Na2CO (a) 2NaCl(a) ; H2O(l) ; CO2(g)


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(b) Molar mass of Na2CO.+H2O $ % ; 12 ; ; 1+ $ 10% ; 1+

Concentration of so!ium carbonate in mol l&1 $ 0.05

Concentration of so!ium carbonate in g l &1 $ .15 > $ 12.%

Mass of 0.05 moles of Na2CO.+H2O $ 12.% g

Molar mass of Na2CO.+H2O $ 12.% , 0.05 g mol&1

$ 20 g mol&1

10% ; 1+ $ 20

1+ $ 16

+ $ 3.6

(c) Molar mass of h*!rate! so!ium carbonate $ 20 g mol&1

=ercentage of ater of cr*stallisation in the compoun! $ 16 x 100 , 209 $ %2.19

Question 53

/n a titration7 25 cm of a potassium h*!ro+i!e solution reuire! 26 cmof a 0.12 M sulfuric

aci! solution for complete neutralisation. Calculate the concentration of the potassium

h*!ro+i!e solution in (a) mol l&1(b) g l&1. -he euation for the reaction is

H24O(a) ; 2"OH(a) "24O(a) ; 2H2O(l)

Answer:

(a)1xM1xn2 $ 2xM2xn1

26x0.12x 2 $25x M2x1

M2 $ 26x0.12x 2, (25x 1)

$ 0.2532 mol l&1

Concentration of potassium h*!ro+i!e solution $ 0.2% mol l&1

(b) Molar mass of potassium h*!ro+i!e $ 5% g mol&1

Concentration of "OH $ 0.2% x5% g l&1$ 1.% g l&1

Question 5!

/n a titration7 20 cm of 0.1 M potassium h*!ro+i!e solution reuire! 25 cmof a h*!rochloric

aci! solution for complete neutralisation. Calculate the concentration of the h*!rochloric aci!

solution in (a) mol l&1(b) g l&1. -he euation for the reaction is


Answer:

(a) 1xM1xn2 $ 2xM2xn1

25xM1x 1 $20x 0.1x1

12


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M1 $ 20x0.1x 1 , (25x 1)

$ 0.0 mol l&1

Concentration of h*!rochloric aci! solution $ 0.0 mol l&1

(b) Molar mass of h*!rochloric aci! $ %.5 g mol&1

Concentration of HCl $ 0.0 > %.5 g l&1$ 2.32 g l&1

Question 56

/n a titration7 25 cm of a so!ium carbonate solution reuire! 22 cmof a 0.1 M h*!rochloric

aci! solution for complete neutralisation. Calculate the concentration of the so!ium carbonate

solution in (a) mol l&1(b) g l&1. -he euation for the reaction is?


Answer:

(a)

1xM1xn2 $ 2xM2xn1

22x0.1x 1$25x M2x2

M2$ 22x0.1x 1 , (25x 2)

$ 0.0 mol l&1

Concentration of so!ium carbonate solution $ 0.0 mol l&1

(b) Molar mass of so!ium carbonate $ 10% g mol&1

Concentration of so!ium carbonate solution $ 0.0 x10% g l&1$ .%% g l&1

Question 57

What olumeof 0.01 M so!ium h*!ro+i!e solution is reuire! to neutralise 20 cmof a

h*!rochloric aci! solution containing 0.6 g of h*!rogen chlori!e per 250 cm of solution#



Answer:

0.6 g of h*!rogen chlori!e per 250 cm of solution is euialent to 0.6 x g l&1$ 2.32 g l&1$

2.32 , %.5 mol l&1$ 0.0 mol l&1

1xM1xn2 $ 2xM2xn1

20x0.0 x 1$2x 0.01 x1

2$ 20x 0.0 x1 , (0.01x 1)

$ 1%0 cmof h*!rochloric aci!

1


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Question 58

What olumeof a 0.01 M so!ium carbonate solution is reuire! to neutralise 25 cmof a

solution containing 0.3 g l&1of sulfuric aci!# -he euation for the reaction is

H24O(a) ; Na2CO(a) Na24O(a) ; H2O(l) ; CO2(g)

Answer:

Concentration of sulfuric aci! solution $ 0.3 g l&1$ 0.3 , 3 mol l&1$ 0.01 mol l&1

1xM1xn2 $ 2xM2xn1

25x0.01 x 1$2x 0.01 x1

2$ 25x 0.01 x1 , (0.01x 1)

$ 25 cmof so!ium carbonate solution

Question 59

/n a titration7 25 cm of a 0.1 M so!ium h*!ro+i!e solution reuire! 2 cmof a sulfuric aci!

solution for complete neutralisation. Calculate (a) the number of moles of so!ium h*!ro+i!e

consume! (b) the number of moles of sulfuric aci! consume! an! (c) the concentration of the

sulfuric aci! solution in mol l&1. -he euation for the reaction is


Answer:

(a) /n the titration7 25 cm of 0.1 M NaOH solution ere use!.

17000 cm

of 0.1 M NaOH solution contains 0.1 moles.25 cmof 0.1 M NaOH solution contains 0.1 X 25 , 17000 moles

$ 0.0025 moles



One mole of H24Oreacts ith to moles of NaOH.

0.0025,2 moles $ 0.00125 moles of H24Oreact ith 0.0025 moles of NaOH.

-he number of moles of sulfuric aci! consume! is 0.00125 moles.

(c) /n 2 cmof the H24O solution there are 0.00125 moles of H24O

/n 17000 cmof the H24O solution there are

0.00125X 17000 , 2 moles $ 0.05 moles

Concentration of the H24Osolution $ 0.05 mol l&1

Question 60

4o!ium h*!rogencarbonate solution reacts ith h*!rochloric aci! solution accor!ing to the

euation

HCl(a); NaHCO(a) NaCl(a) ; H2O(l) ; CO2(g)

1


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/t as foun! that 25 cm of a solution containing . g l&1reacte! ith 26 cm of a solution of

h*!rochloric aci!. Calculate the concentration of the h*!rochloric aci! solution in (a) mol l&1

(b) g l&1.

Answer:

(a)

Concentration of so!ium h*!rogencarbonate solution $ . g l&1$ . , mol l&1$ 0.1 mol l&1

1xM1xn2 $ 2xM2xn1

26xM1x 1$25x 0.1 x1

M1$ 25x 0.1 x1 , (26x 1)

$ 0.03 mol l&1

(b) Concentration of h*!rochloric aci! solution $ 0.03 mol l&1$ 0.03 x%.5 mol l&1

$ .3 g l&1

15

worked solutions ch. 11

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