Najinder, a 56-year-old man, was rushed to hospital by his wife as he was having
ID: 3473632 • Letter: N
Question
Najinder, a 56-year-old man, was rushed to hospital by his wife as he was having a severe asthma attack. Blood tests showed that the pH of Najinder's blood was 7.15 (normal blood pH range is 7.35 -7.45). The drop in pH was due to an increase in blood CO_2 levels. What is the pH scale? The pH scale is logarithmic. What is a logarithmic scale? What therefore can you deduce about a solution of pH5 compared to a solution of pH6? What is the pH of a neutral solution? What makes it neutral? What happens when an acid is mixed with water? What is the role of a buffer system? How do buffer systems work? When CO_2 is mixed with water it forms a buffer Explain and state the formula that shows what happens when carbon dioxide is mixed with water. Najinder's asthma has led to an airway obstruction, inefficient gas exchange, and excess co2 building up in his blood. Using the formula that you gave in answer to question 6, explain why Najinder's blood pH has dropped.Explanation / Answer
1. pH stands for potential of hydrogen which measures either acidity or alkalinity of water soluble substances. The range varies from 1 to 14 and the value of 7 is considered as neutral. Any value going below 7 is considered as acidic and any value above 7 is considered as alkaline.
2. The logarithmic scale of pH essentially describes the difference in 1 pH unit is a difference of 10 times. On a pH scale, a solution of pH 5 is 10 times more acidic than a solution of pH 6.
3. A solution having a pH of 7 is considered as a neutral solution. It is the point where both hydrogen ion and hydroxide ion activity are equal.
4. When acid is mixed with water, the acid dissociates hydrogen ion present and accompanied by large amounts of energy. This energy is used for the hydration reaction of sulfuric acid ions.
5. A buffer is a mixture of molecules that act to keep the pH of the solution close to neutral. They act as absorbers which can nullify any excess amount of hydrogen or hydroxide ions. A buffer is a solution that can resist pH change upon the addition of acidic or basic components. It is able to neutralize small amounts of added acid or base, thus maintaining the pH of the solution relatively stable.
6. When carbon dioxide is mixed with it undergoes hydrolysis to form carbonic acid.
CO2 + H2O -------> H2CO3
7. When there is build up of carbon dioxide in the blood, it readily mixes with water and forms carbonic acid. It is a weak acid but still able to make the pH of the blood drop lower than the physiological pH.
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