Question

A cup of coffee has a hydrogen ion concentration of $\text{7}\text{.6 }\times \text{ 1}{{\text{0}}^{-6}}\text{M}$. What is the pH of the coffee?
A. 5.88
B. 5.12
C. 7.60
D. 4.12

Answer 1

For this problem, we have to take the log of the given concentration of the hydrogen to calculate the pH of the cup coffee. After which we can choose the correct option among the given options.

Complete step by step solution:
- In the given question, we have to calculate the pH of the solution of the cup of coffee from the given concentration of hydrogen.
- As we know that pH is defined as the power of the hydrogen which is also defined as the negative logarithm of the concentration of the hydrogen.
- The expression can be written as:
$\text{pH = -log}{{\text{H}}^{+}}$ …. (1)
- It is given that the concentration of the hydrogen is $\text{7}\text{.6 }\times \text{ 1}{{\text{0}}^{-6}}\text{M}$ so by putting the value in the equation (1) we will get:
$\text{pH = -log(}~7.6\text{ }\times \text{ 1}{{\text{0}}^{-6}}\text{)}$ ….(2)
- The expression (2) can also be written as:
$\text{pH = -log}7.6\text{ - log1}{{\text{0}}^{-6}}$
$\text{pH = 6 - log7}\text{.6 = 5}\text{.12}$
- So, the pH of the cup of coffee will be 5.12 which indicates that the solution is slightly acidic.
- Whereas most of the coffees are acidic by nature whose pH varies from 4.85 to 5.10.
- The acidic nature of the coffee does not alter the pH of the urine but if consumed in large amounts then it may cause discomfort in the body.

Therefore, option B is the correct answer.

Note: Due to the acidic nature of coffee it can adversely affect the body of human beings if consumed in large amounts. The harmful effect of coffee includes discomfort in digestion, triggered level of acid in the stomach which causes burning effects and vomiting.