What is the pH of 9.01 x 10^-4 M Mg(OH)2

What is the pH of 2.33 x 10^-2M of NH4OH

A. 11.26

B. 12.37

Explanation:

A. Step 1:

Dissociation of Mg(OH)2. This is illustrated below below:

Mg(OH)2 <==> Mg2+ + 2OH-

A. Step 2:

Determination of the concentration of the OH-

From the above equation,

1 mole of Mg(OH)2 produce 2 moles of OH-

Therefore, 9.01x10^-4 M Mg(OH)2 will produce = 9.01x10^-4 x 2 = 1.802x10^-3 M of OH-

A. Step 3:

Determination of the pOH. This is illustrated below:

pOH = - Log [OH-]

[OH-] = 1.802x10^-3 M

pOH = - Log [OH-]

pOH = - Log 1.802x10^-3

pOH = 2.74

A. Step 4:

Determination of the pH.

pH + pOH = 14

pOH = 2.74

pH + 2.74 = 14

Collect like terms

pH = 14 - 2.74

pH = 11.26

B. Step 1:

Dissociation of NH4OH. This is illustrated below below:

NH4OH <==> NH4+ + OH-

B. Step 2:

Determination of the concentration of the OH-

From the above equation,

1 mole of NH4OH produce 1 moles of OH-

Therefore, 2.33x10^-2M of NH4OH will also produce 2.33x10^-2M of OH-

B. Step 3:

Determination of the pOH. This is illustrated below:

pOH = - Log [OH-]

[OH-] = 2.33x10^-2M

pOH = - Log [OH-]

pOH = - Log 2.33x10^-2M

pOH = 1.63

B. Step 4:

Determination of the pH.

pH + pOH = 14

pOH = 1.63

pH + 1.63 = 14

Collect like terms

pH = 14 - 1.63

pH = 12.37