Question

A solution is made by adding 0.380 gg Ca(OH)2(s)Ca(OH)2(s), 50.0 mLmL of 1.45 MM HNO3HNO3, and enough water to make a final volume of 75.0 mLmL. Part A Assuming that all of the solid dissolves, what is the pH of the final solution

Answer 1

Answer: pH of the final solution is 0.08

Explanation:

To calculate the moles, we use the equation:

a) moles of $Ca(OH)_2$ =$\text{Number of moles}=\frac{\text{Given mass}}{\text {Molar mass}}=\frac{0.380g}{74g/mol}=0.0051moles$

b) To calculate the number of moles for given molarity, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}\times 1000}{\text{Volume of solution (in L)}}$  

Molarity of $HNO_3$ solution = 1.45 M

Volume of solution = 50.0 mL

$1.45M=\frac{\text{Moles of}HNO_3\times 1000}{50.0ml}\\\\\text{Moles of }HNO_3=\frac{1.45mol/L\times 50.0}{1000}=0.0725mol$

$Ca(OH)_2+2HNO_3\rightarrow Ca(NO_3)_2+2H_2O$

1 mole of $Ca(OH)_2$ reacts with 2 moles of $HNO_3$

Thus 0.0051 moles of $Ca(OH)_2$ reacts with =$\frac{2}{1}\times 0.0051=0.0102$ moles of $HNO_3$

Moles of $HNO_3$ left = (0.0725-0.0102) = 0.0623

Thus 0.0623 moles of $H^+$ are left in 75.0 ml of solution

Molarity of $H^+=\frac{moles\times 100}{\text {Volume in ml}}=\frac{0.0623\times 1000}{75.0}=0.83M$

pH is the measure of acidity or alkalinity of a solution.

pH is calculated by taking negative logarithm of hydrogen ion concentration.

$pH=-\log [H^+]$

$pH=-\log[0.83]$

$pH=0.08$

Thus pH of the final solution is 0.08

Answer 2

The pH given by the final solution would be as follows:

0.08

What is pH?

The pH is described as the measurement that is employed to denote the level of acid, as well as, base.

Given that,

Amount of Ca(OH)2(s) = 0.380 g

Amount of HNO3 = 50 ml

Final volume $= 75 ml$

It is given that,

The entire solid dissolves,

The pH of the final solution can be determined by finding the ion concentration and number of moles:

No. of Ca(OH)2 moles

= Mass given/Molar mass

= 0.380/74

= 0.0051 moles

No. of HNO3 moles,

= Mass given/Molar mass

= 1.45 × 50.0)/1000

= 0.725 moles

The reaction provided by them is:

$Ca(OH)_{2} + 2HNO_{3}$ → $Ca(NO_{3})_{2} + 2H_{2} O$

Now,

Molarity of HNO3 $= (0.0623$ × $1000/75)$

$= 0.83 M$

By employing negative logarithm,

pH $= - log|(0.83)|$

∵ $pH = 0.08$

Thus, 0.08 is the correct answer.

Learn more about "pH" here:

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