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1. Calculate the value of [OH] from the given [H3O+] in each solution and label

ID: 497146 • Letter: 1

Question

1. Calculate the value of [OH] from the given [H3O+] in each solution and label the solution as acidic or basic:

(a) [H3O+] = 4.0 × 10^11 M        (b) [H3O+] = 3.3 × 10^3 M.

(a) ____ x10 ____ M, acidic or basic

(b) ____ x10 ____ M, acidic or basic

2. Calculate the value of [OH] from the given [H3O+] in each solution and label the solution as acidic or basic:

(a) [OH] = 3.8 × 10^10 M          (b) [OH] = 7.3 × 10^3 M.

(a) ____ x10 ____ M, acidic or basic

(b) ____ x10 ____ M, acidic or basic

3. Calculate the value of [OH] from the given [H3O+] and label the solution as acidic or basic.

(a) 7.8 × 10^2 M           (b) 1.8 × 10^9 M

(a) ____ x10 ____ M, acidic or basic

(b) ____ x10 ____ M, acidic or basic

4. What H3O+ concentration corresponds to each pH value: (a) 10.200   (b) 8.700   (c) 3.600?

(a)   ____ x10 ____ M

(b) ____ x10 ____ M

(c)    ____ x10 ____ M

5. Convert each H3O+ concentration to a pH value.

(a) 4.6 × 10^4 M        (b) 6.24 × 10^8 M

Explanation / Answer

Answer :

Ionic Product of Water = [H3O+][HO-] = 1 x 10-14.

Criteria for nature of solution :

If, [H3O+] > [HO-] then Solution is Acidic.

If, [H3O+] = [HO-] then Solution is Neutral..

If [H3O+] < [HO-] then Solution is Basic.

1)

a)  [H3O+] = 4.0 x 10-11 M

By eq.(1),  

[HO-] = 1.0 x 10-14 / [H3O+]

= 1.00 x 10-14 / 4.0 x 10-11

[HO-]= 2.5 x 10-4 M.

[H3O+] < [HO-] then Solution is Basic.

b)  [H3O+] = 3.3 x 10-3 M

By eq.(1),  

[HO-] =  1.0 x 10-14 / [H3O+]  

= 1.00 x 10-14 / 3.3 x 10-3

[HO-]= 3.03 x 10-12 M.

[H3O+] > [HO-] then Solution is Acidic.

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2)

a)  [HO-] = 3.8 x 10-10 M

By eq.(1),  

[H3O+] = 1.0 x 10-14 / [HO-]

= 1.00 x 10-14 / 3.8 x 10-10

[H3O+]= 2.63 x 10-5 M.

[H3O+] > [HO-] then Solution is Acidic.

b)  [HO-] = 7.3 x 10-3 M

By eq.(1),  

[H3O+] =  1.0 x 10-14 / [HO-]  

= 1.00 x 10-14 / 7.3 x 10-3

[H3O+]= 1.37 x 10-12 M.

[H3O+] < [HO-] then Solution is Basic.

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3)

a)  [H3O+] = 7.8 x 10-2 M

By eq.(1),  

[HO-] = 1.0 x 10-14 / [H3O+]

= 1.00 x 10-14 / 7.8 x 10-2

[HO-]= 1.28 x 10-13 M.

[H3O+] > [HO-] then Solution is Acidic.

b)  [H3O+] = 1.8 x 10-9 M

By eq.(1),  

[HO-] =  1.0 x 10-14 / [H3O+]  

= 1.00 x 10-14 / 1.8 x 10-9

[HO-]= 5.56 x 10-6 M.

[H3O+] < [HO-] then Solution is Basic.

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4)

pH = -log[H3O+]

[H3O+] = 10-pH.

a) pH = 10.200

[H3O+] = 10-pH.= 10-10.200 = 6.31 x 10-11.

[H3O+] = 6.31 x 10-11 M

b)

pH = 8.700

[H3O+] = 10-pH.= 10-8.700 = 2.00 x 10-9.

[H3O+] = 2.00 x 10-9 M

c)

pH = 3.600

[H3O+] = 10-pH.= 10-3.600 = 2.51 x 10-4.

[H3O+] = 2.51 x 10-4 M

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5)

pH = -log[H3O+]

a) [H3O+] = 4.6 x 10-4 M.

pH = -log(4.6 x 10-4)

pH = 3.34

b) [H3O+] = 6.24 x 10-8 M.

pH = -log(6.24 x 10-8)

pH = 7.20

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