What is the pH of a 0.00001 molar HCl solution?

Question

Select one:

a. 

9

b. 

4

c. 

5

d. 

1

Answer 1

Lets first convert 0.00001 to scientific notation to simply things out.

Thus 0.00001 = 1 X10^-5 = 10^-5

We know that pH of the solution is the negative logarithm of the concentration of hydrogen ions or hydronium ions. pH= = log [ H+]

We are told the solution is acidic because HCl is an acid so we have the concentration of H+.

Thus, if we plug in the concentration to the above equation we get

pH= - log [ 10^-5]

according to the law of logarithm of the exponents, we know that if the base is the same as the base of the logarithm is equal to the exponent. (in this case the base is 10. a =10). log_a(a)ⁿ= n

Thus, pH= - log [10^-5] = - (-5). negative times a negative is positive thus the answer is 5.