Question

Which one has high pH value?
(i) Blood or distilled water
(ii) Gastric juice or lemon juice

Answer 1

Hint: A pH scale helps in measuring the acidic and basic substances. Blood is alkaline in nature whereas gastric juice is the acid present in the stomach.

Complete answer:
A pH is the degree of hydrogen ions (H$^ + $) concentration in a solution. It tells the acidic and basic nature of a substance. Water containing free hydrogen ions is said to be acidic whereas water containing free hydroxyl ions is called basic or alkaline. The pH ranges from 0 to 14. The pH below 7 (0.0 to 6.9) indicates acidity and pH above 7 (7.1 to 14.0) indicates alkaline or basic. 7 being neutral in nature. It is found that high concentration of hydrogen ions has low pH value and are acidic in nature whereas lower levels of hydrogen ions have high pH value and are basic in nature. But the overall concentration of hydrogen is inversely related to the pH and is a degree of pH scale.
Distilled water is achieved by the distillation process in which all the ions present in water are removed resulting in the purest form of water. So the pH of pure water is 7.0. It is neither acidic nor basic in nature.
Blood is alkaline or basic in nature. The pH ranges from 7.35 to 7.45. The normal balance of pH is maintained by lungs and kidney. As lungs help in removing $c{o_2}$ from the body via breathing whereas the kidney removes acids via urine. So the pH of blood is higher than the distilled water. Gastric juice is produced by the parietal cells of the stomach. It makes the medium acidic due to the presence of HCl. It is maintained acidic so that the stomach enzymes (pepsin) can work in an acidic environment. So the pH of gastric juice is 1.0 to 1.5.
Lemon juice is composed of two acids. The juice has tart flavour and ascorbic acid. Lemons are acidic in nature so that pH ranges from 2 to 3.
So the pH of lemon juice is higher than gastric juice.

Therefore the correct option is (i) Distilled water or blood.

Note: The disturbance in the pH of blood results in acidosis and alkalosis. Acidosis occurs when there is high concentration of acid in the blood resulting in the reduction of blood pH. Alkalosis occurs when there is high concentration of base in the blood resulting in the increase of pH.