Question

Suppose you are given some concentrated HCl which is labelled $11.6M$HCl. You wish to make it $200ml$ of pH $1.25.$ What amount (in ml to the nearest integer) of HCl is needed?

Answer 1

At first will write what is given in the question. Then we will calculate the molarity hydrogen ion in the solution HCl. Then we will equal the concentration initial multiplied by volume to the final concentration multiplied by the final volume. Then we will get the initial volume needed. Then we will round it off to the nearest integer. In the end we will write the answer.

Complete step-by-step solution: Step1. The initial concentration of the HCl = $11.6M$
Final volume= $200ml$
The pH of the solution= $1.25$
We need to find the volume of the HCl
Step2:We need to find the concentration of the hydrogen ion. The hydrogen will be provided by the HCl. The molarity will be calculated by the formula ${H^ + } = {10^{ - pH}}$
So the ${H^ + } = {10^{ - 1.25}} = 0.056$M
Step 3.The initial concentration multiplied by the initial volume is equal to the initial concentration into final volume. There is no change in the moles.
${C_i} \times {V_i} = {C_f} \times {V_f}$
$0.056 \times 200 = 11.6 \times {V_i}$
The initial volume will be $0.965ml$
Step4. Now we need to round it off to the nearest integer. So the first decimal place is nine which is greater than five. So it will be rounded off to the $1ml$. Hence we need $1ml$ of the volume of HCl.

Note: The nature of the solution can be found out by the litmus test. The blue litmus paper turns into red under acidic solution, and the red litmus paper turns into the blue under basic conditions.When the solution is acidic than pH will be less than seven and when solution is basic than the pH will be more than seven.