Question 1 What mass of HClO 4 should be present in 0.500 L of solution to obtai

Question

Question 1

What mass of HClO4 should be present in 0.500 L of solution to obtain a solution with pH = 0.5?

 a) 0.32 g

 b) 0.64 g

 c)16 g

 d) 1.6 g

Question 2

  0.085 M HA solution has a percent ionization of 0.59%. Determine the Ka value. 

a)   3.61 x 10-5            

b) 3.5 x 10-4

 c) 1.8 x 10-5

d) 3.0 x 10^6

Question 3

  Which of the following is not a basic salt

a)  NaCl

b)  KClO

c)  KCN

d)  NaCN

 
Question 4

Which one is a lewis acid in the reaction… Fe3+(aq) + 6 H2O(l)    Fe(H2O)63+(aq)

a)  None

b) Fe3+

c)  H2O            

d)   Fe(H2O)63+

Question 5

  Calculate [H3O+] and [OH-] respectively for pH = 8.55. 

a)   2.2 x 10-6 M and 1.7 x 10-3 M

b)   2.8 x 10-9 M and 3.6 x 10-6 M

c)   8.55 x 10-7 M and 5.45 x 10-7 M

d)   8.55 M and 5.45 M

Explanation / Answer

Question 1

What mass of HClO4 should be present in 0.500 L of solution to obtain a solution with pH = 0.5?

Solution :- HClO4 is the strong acid therefore the concentration of the H+ is same as concentrationof the HClO4

Lets find the [H+] using the given pH

[H+] = anitlog [-pH]

        = antilog [-0.5]

        = 0.316 M

So the concentration of the HClO4 is 0.316 M

Lets find the moles

Moles = molarity * volume

          = 0.316 mol per L * 0.500 L

          = 0.158 mol

Now lets find the mass of HClO4

Mass of HClO4 = moles * molar mass

                           = 0.158 mol * 100.46 g per mol

                           = 16.0 g HClO4

So the answer is option C

Question 2

  0.085 M HA solution has a percent ionization of 0.59%. Determine the Ka value.

Solution :- lets find the concentration of the H+ using the % ionization

% ionization = (x/initial concentration )*100%

x= 0.59 % * 0.085 M / 100 %

= 0.000502 M

Now lets calculate the ka

Ka = [x]^2 / [0.085-x]

Ka= [0.000502]^2 / [0.085-0.000502]

Ka = 2.97*10^-6 so we can round it to 3.0*10^-6

Answer will be option d

Question 3

  Which of the following is not a basic salt

solution :- NaCl is not basic salt because it is salt of strong acid and strong base so its neutral salt

so the answer is option A

Question 4

Which one is a lewis acid in the reaction… Fe3+(aq) + 6 H2O(l) Fe(H2O)63+(aq)

Solution :- Lewis acid is electron pair acceptor so the Fe^3+ is accepting electrons so the Fe^3+ is lewis acid

So the answer is option   B

Question 5

  Calculate [H3O+] and [OH-] respectively for pH = 8.55.

solution :-

[H3O+] = antilog [-pH]

             = antilog [ - 8.55]

            = 2.8*10^-9

[OH-] = Kw/[H3O+]

          = 1*10^-14 / 2.8 *10^-9

         = 3.6*10^-6

So the answer is option B  

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