Sunday, July 14, 2019

Solution for the mathematical Problems


Solution to the
Mathematical
Problems

Chapter:  Solution
Book: Essentials of physical chemistry
(Multicolor Edn. 2009)

Prepared By
Md. Imran Nur Manik
Lecturer
Department of Pharmacy
Northern University Bangladesh

Solution for the mathematical Problems
Chapter:  Solution 
Book: Essentials of physical chemistry (Multicolor Edn. 2009)

By-Md. Imran Nur Manik, Lecturer, Pharmacy, NUB
Using the formula: W=(SMV÷1000)
  
Problem 1. [5(b); Page 551]  Determine the molality of a solution containing 86.53 g of sodium carbonate (mol mass = 105.99 gm) per litre in water at 20°C. The density of the solution at this temperature is 1.0816 g mL–1


Now putting these values in the equation (i)
we get, 
        
                 
So , Molality of the final solution is 0.75447 m.

Here, 
The amount of solute, W=86.53 gm
Molecular weight of solute, M=105.9 g/mol

Density of the solution, D= 1.0816 gm/mL
That means, 1 mL solution = 1.0816 gm
                    So, 1L solution = (1.0816× 1000) gm 
                                            = 1081.6 gm.

Therefore,
The amount of the final solvent, V = 1081.6 gm
Molality of the Solution,              S=?

Problem 2. [7(a) ; Page 551]  What is molarity and molality of a 13% solution (by weight) of H2SO4. It’s density is 1.09 g/mL.

Determination of Molarity

Now putting these values in the equation (i)
we get, 
        
                 
So , Molarity of the final solution is 1.4459 M
Here, 
The amount of solute, W=13 gm
Molecular weight of solute, M=98 g/mol

Density of the solution, D= 1.09 gm/mL
That means, 1.09 gm solution = 1mL
                So, 100 gm solution = (100÷1.09) mL
                                                = 91.743 mL

Therefore,
The volume of the final solution, V = 91.743 mL
Molarity of the Solution,              S=?
                                                 
Determination of Molality

Now putting these values in the equation (i)
we get, 
        
                 
So , Molality of the final solution is 1.52474m
Here,    
The amount of solute, W=13 gm
Molecular weight of solute, M=98 g/mol

The solution is 13% by weight.
That means,  the amount of solvent = (100÷13) gm
                                                        = 87 gm
Therefore,

The amount of the final solvent, V = 87 gm

Molality of the Solution,              S=?

Problem 3. [8 ; Page 551]  Calculate the molality of a solution of sodium hydroxide which contains 0.2 g of sodium hydroxide in 50 g of the solvent.

Now putting these values in the equation (i)
we get, 
        
                 
So , Molality of the final solution is 0.100 m

Here,
The amount of solute, W=0. 2 gm

Molecular weight of solute, M=40 g/mol

The amount of the final solvent, V = 50 gm 

Molality of the Solution,              S=?

Problem 4. [9 ; Page 551]  Calculate the normality of a solution containing 6.3 g of oxalic acid crystals (Mol. wt. 126) dissolved in 500 mL of solution.

Now putting these values in the equation (i)
we get, 
        
                 
So , Normality  of the final solution is 0.200 N
Here, 
The amount of solute, W=6.3 gm
Molecular weight of solute       =126 g/mol

Equvalent weight of solute, M=(126÷2) gm
  =63 gm

The volume of the final solution, V = 500 mL

Normality of the Solution,              S=?


Problem 5. [11(a); Page 551]  49 g of H2SO4 are dissolved in 250 mL of solution. Calculate the molarity of the solution.

Now putting these values in the equation (i)
we get, 
        
                 
So , Molarity of the final solution is 2.00M
Here, 
The amount of solute, W=49 gm
Molecular weight of solute , M=98 g/mol


The volume of the final solution, V = 250 mL

Molarity of the Solution,              S=?

Problem 6. [11(b); Page 551]  45 g of glucose, C6H12O6, are dissolved in 500 g of water.Calculate molality of the solution.

Now putting these values in the equation (i)
we get, 
        
                 
So , Molality of the final solution is 0.500m
Here, 
The amount of solute, W=45 gm
Molecular weight of solute , M=180 g/mol


The amount of the final solvent, V = 500 gm

Molality of the Solution,              S=?

Problem 7. [25(b); Page 552]  A sample of spirit contains 92% of ethanol by weight
the rest being water. What is the mole fraction of its constituents?

Solution: Let the mass of solution be 100 gm 
Since it contains 92% of ethanol by weight so the wight of ethanol is 92 gm  and that of water is 8 gm. 
Now , no. of moles of ethanol=(92 ÷ 46) mole =2 mole
   no. of moles of water = (8 ÷ 18) mole = 0.444 mole
Total moles of solution= (2+0.444) mole = 2.444 mole
Therefore, the mole fraction of ethanol= (2÷2.444) = 0.818
      And the mole fraction of water = (0.444÷2.444) = 0.1816~0.182
Mole fraction of ethanol= 0.818 and water= 0.182.

Problem 8. [27 ; Page 552]  5 g of NaCl is dissolved in 1 kg of water. If the density of the solution is 0.997 g mL–1, calculate the molarity, normality, molality and mole fraction of the solute.

Determination of Molarity

Now putting these values in the equation (i)
we get, 
        
                 
So , Molarity of the final solution is 0.0847 M
Here, 
The amount of solute, W=5 gm
Molecular weight of solute, M=58.5g/mol
Total amount of solution=(1000+5) gm=1005 gm
Density of the solution, D= 0.997 gm/mL
That means, 0.997 gm solution = 1mL
                So, 1005 gm solution = (100÷1.09) mL
                                                = 1008.024072 mL

Therefore,
The volume of the final solution, V = 1008.024 mL
Molarity of the Solution,              S=?
Determination of Molality

Now putting these values in the equation (i)
we get, 
        
                 
So , Molality of the final solution is 0.08547 m

Here, 
   
The amount of solute, W=5 gm

Molecular weight of solute, M=58.5 g/mol


The amount of the final solvent, V = 1000 gm

Molality of the Solution,              S=?
Determination of Normality

We know N=nM ; Thus ,N=1×0.0847 (Where n is the equivalent number of NaCl=1
And, M is the Molarity of the solution= 0.0847 , Known earlier )
So, Normality of the solution=0.0847 N
Determination of Mole Fraction
Here no. of moles of solute, NaCl=(5÷58.5)mole = 0.0855 mole
 And no. of moles of  Solvent, H2O = (1000÷18) mole = 55.5 mole
Total moles of solute and solvent = (0.0855+55.5) mole = 55.5855 mol.
Mole fraction of NaCl = (0.0855÷ 55.5855) =0.001538.    (ans.)
Problem 9. [29 ; Page 552]  Calculate the molarity and normality of a solution containing 5.3 g of Na2CO3 dissolved in 1000 mL solution.
Determination of Molarity

Now putting these values in the equation (i)
we get, 
        
                 
So , Molarity of the final solution is 0.050 M

Here, 

The amount of solute, W=5.3  gm

Molecular weight of solute, M=106 g/mol

The volume of the final solution, V = 1000 mL

Molarity of the Solution,              S=?
Determination of Normality

Now putting these values in the equation (i)
we get, 
        
                 
So , Normality of the final solution is 0.10 N
Here, 
   
The amount of solute, W=5 gm

Molecular weight of solute      =106 g/mol

Equivalent weight of the solute, M=(106÷2) gm
                                                          =53 gm

The volume of the final solvent, V = 1000 mL

Normality of the Solution,              S=?
Determination of Normality from Molarity

We know N=nM ; Thus ,N=2×0.05 (Where n is the equivalent number of Na2CO3=2
And, M is the Molarity of the solution= 0.05 , Known earlier )
So, Normality of the solution=0. 10 N
Problem 10. [28 ; Page 552]  Calculate the amount of Na+ and Cl ions in grams present in 500 mL of 1.5 M NaCl solution.

Solution:   We know, Molecular weight of NaCl= 58.5 gm Where, M.Wt. of Na+ = 23g & Cl= 35.5g

Therefore the amount of Na+ ions in grams present=17.25 gm

Therefore the amount of Cl ions in grams present=26.625 gm
Problem 11. [30; Page 552]  Calculate the molarity of a solution containing 331g of HCl dissolved in sufficient water to makes 2dm3 of solution.

Now putting these values in the equation (i)
we get, 
        
                 
So , Molarity of the final solution is 4.534 M

Here, 

The amount of solute, W=331 gm
Molecular weight of solute , M=36.5 g/mol


The volume of the final solvent, V = 2000 mL

Molality of the Solution,              S=?

Problem 12. [33; Page 552]  What is the normality of a solution containing 28.0 g of KOH dissolved in sufficient water to make 400 ml of solution?

Now putting these values in the equation (i)
we get, 
        
                 
So , Normality of the final solution is 1.2478 N

Here, 

The amount of solute, W=28 gm
Molecular weight of solute      =56.1 g/mol

Equivalent weight of the solute, M=(56.1÷1) gm
                                                          =56.1 gm

The volume of the final solvent, V = 400mL

Normality of the Solution,              S=?

Problem 13. [34 ; Page 552]  A 6.90 M solution of KOH in water contains 30% by weight of KOH. Calculate the density of the solution.
Solution:
Here, 
The amount of solute, W=30 gm
Molecular weight of solute, M=56.1 gm/mol
Molarity of the Solution,              S=6.90 M
The volume of the final solution, V = ?
Now putting these values in the equation (i)  we get, 
         
Therefore the volume of the solution= 77.5013 mL
And the total amount of solution= 70+30= 100gm.     

So the density of the solution=1.29 gm/mL
Problem 14. [28 ; Page 556]  36 g of glucose (molecular mass 180) is present in 500 g of water, find out the  molality of the solution .

Now putting these values in the equation (i)
we get, 
        
                 
So , Molality of the final solution is 0.40 m

Here, 
   
The amount of solute, W=36 gm

Molecular weight of solute, M=180 g/mol


The amount of the final solvent, V = 500 gm

Molality of the Solution,              S=?

Problem 15. [30 ; Page 556]  Find out  the mole fraction of ethyl alcohol in a solution containing 36 g of H2O and 46 g of ethyl alcohol. 

Solution: Here, moles of water = (36÷18) mole = 2 moles
 Moles of ethyl alcohol = (46÷46) mole =1 mole
Total moles of the solution = (2+1) mole= 3 moles
So, mole fraction of ethyl alcohol =13 (ans.)
Problem 16. [32 ; Page 556]  Calculate the molarities of 0.1N solution of  HCl and 0.1N solution of H2SO4.

Solution:  We know N=nM  
Here, N= Normality of the final solution, M= Molarity of the final solution and n= Equivalent number of the solute
Determination of Molarity of 0.1N solution of  HCl 
We know N=nM ; Thus ,0.1=1×M (Where n is the equivalent number of HCl=1
And, N is the Normality of the solution= 0.1 , Known earlier )
So, Molarity of the solution=0. 10 M
Determination of Molarity of 0.1N solution of  H2SO4 
We know N=nM ; Thus ,0.1=2×M (Where n is the equivalent number of H2SO4=2
And, N is the Normality of the solution= 0.1 , Known earlier )
So, Molarity of the solution=0. 05 M
Problem 17. [32 ; Page 556]  Find out the amount required for the preparation of 100ml of 0.1N H2SO4

Now putting these values in the equation (i)
we get, 
        
                 
So , The amount of acid needed is 0.490 gm
Here, 
The amount of solute, W=?
Molecular weight of solute      =98 g/mol

Equivalent weight of the solute, M=(98÷2) gm
                                                          =49 gm

The volume of the final solvent, V = 100mL

Normality  of the Solution,              S=0.1N

Problem 18. [34 ; Page 556]  How many grams of glucose are present in 100 mL of 0.1 M solution

Now putting these values in the equation (i)
we get, 
        
                 
So , The amount of glucose needed is 1.800 g
Here, 

The amount of solute, W=?

Molecular weight of solute      =180g/mol

The volume of the final solvent, V = 100mL

Molarity of the Solution,              S=0.1M

Problem 19. [38 ; Page 557]  49 g of H2SO4 is dissolved in 250 mLof the solution, find out the  molarity of the solution .

Now putting these values in the equation (i)
we get, 
        
                 
So , Molarity of the final solution is 2.00M

Here, 
   
The amount of solute, W=49 gm

Molecular weight of solute, M=98g/mol


The volume of the final solvent, V = 250 mL

Molarity of the Solution,              S=?
Problem 20. [42 ; Page 557]  What is the total weight of 100 ml of 2 M solution of HCl?

Now putting these values in the equation (i)
we get, 
        
                 
So , The  total amount =(100+7.3)gm=107.3 gm
Here, 

The amount of solute, W=?

Molecular weight of solute      =36.5 g/mol

The volume of the final solvent, V = 100mL
Molarity of the Solution,              S=2 M
The weight of the final solvent = 100 gm

Problem 21. [43 ; Page 557]  1 kg of a solution of CaCO3 contains 1 g of calcium carbonate. What will be the concentration of the solution?

Solution:  
 Here, the amount of solute=1 gm and the total amount of solution =1000 gm
Now putting these values in the equation (i) we get, (1÷1000)=0.001
In terms of ppm the concentration will be =(0.001× 106)= 1000 ppm
Problem 22. [48 ; Page 558]  What is the weight of urea required to prepare 200 ml of 2 M solution?

Now putting these values in the equation (i)
we get, 
        
                 
So , The weight of urea required=24.0 gm
Here, 

The amount of solute, W=?

Molecular weight of solute      =60 g/mol

The volume of the final solvent, V = 200 mL

Molarity of the Solution,              S=2 M

Problem 23. [49 ; Page 558]  What is the molality of a solution prepared by dissolving 9.2 g toluene (C7H8) in 500 g of benzene?

Now putting these values in the equation (i)
we get, 
        
                 
So , Molality of the final solution is 0.200 m

Here, 
   
The amount of solute, W=9.2 gm

Molecular weight of solute, M=92 g/mol


The amount of the final solvent, V = 500 gm

Molality of the Solution,              S=?




1 comment:

  1. Sir,Can you provide the solutions of Nuclear Chemistry and Photochemistry?

    ReplyDelete