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Question

Example 2: Titrate 25.00 mL of 0.100 M HCl with 0.100 M CH3NH2 and determine the pH of the mixture at the following points of the 9tra9on curve:

a. When 10.00 mL of CH3NH2 has been added b. When 25.00 mL of CH3NH2 has been added c. When 35.00 mL of CH3NH2 has been added 

 

Answer 1

Step 1:

25.00  mL of 0.100 M HCL is 2.5 mMOL of .

The chemical reaction of Methylamine reacts with water :

(a)

When 10.00 mL of is added.

25.00  mL of 0.100 M HCL is 2.5 mMOL of .

10.00  mL of 0.100 M is 1 mMOL of .

Number of moles of acid left after reaction :

2.5 mMOL of -  1 mMOL of = 1.5 mMOL of

Find .

Solution :

.

Answer 2

Step 1:

25.00  mL of 0.100 M HCL is 2.5 mMOL of .

The chemical reaction of Methylamine reacts with water :

(b)

When 25.00 mL of is added.

25.00  mL of 0.100 M HCL is 2.5 mMOL of .

25.00  mL of 0.100 M is 2.5 mMOL of .

Number of moles of acid left after reaction :

2.5 mMOL of -  2.5 mMOL of = 0 mMOL of

At equilibrium concentration :

The HCL solution of ionization constant is

Find .

Solution :

.

Answer 3

Step 1:

25.00  mL of 0.100 M HCL is 2.5 mMOL of .

The chemical reaction of Methylamine reacts with water :

(c)

When 25.00 mL of is added.

25.00  mL of 0.100 M HCL is 2.5 mMOL of .

35.00  mL of 0.100 M is 3.5 mMOL of .

Number of moles of base left after reaction :

3.5 mMOL of - 2.5 mMOL of -  = 1 mMOL of

Find .

Solution :

.