Calcium hydroxide, also known as slaked lime, is sometimes used in antacid formulations to neutralize hydrochloric acid in the stomach. While magnesium hydroxide is also a common antacid, the provided answer key identifies calcium hydroxide. Both act as bases to neutralize gastric acid, providing relief from acidity and heartburn.
Lemon juice contains a high concentration of citric acid, making it quite acidic. The pH scale ranges from 0 to 14, where values below 7 indicate acidity. Lemon juice typically has a pH value between 2 and 3, making 2 the most accurate choice provided.
3843
Which of the following substances contains the highest concentration of hydrogen ions (H+)?
Hydrogen ion concentration is inversely related to pH. Gastric juice, which contains hydrochloric acid, typically has a very low pH (around 1.5 to 3.5), indicating a much higher concentration of H+ ions compared to lemon juice (pH ~2-3), milk of magnesia (basic), or sodium hydroxide (strongly basic).
3844
Why is it common agricultural practice to add lime (calcium oxide or calcium hydroxide) to soil?
Agricultural lime is used to neutralize acidic soil. Many crops grow best in soil with a near-neutral pH. If the soil is too acidic, the availability of essential nutrients is reduced and toxic levels of certain metals may increase. Adding lime raises the pH, effectively reducing soil acidity.
3845
How does the continuous application of calcium superphosphate fertilizer affect the pH of the soil?
Calcium superphosphate is generally acidic in nature. Continuous use of acidic fertilizers typically leads to a decrease in soil pH (making it more acidic). Note: The provided answer key suggests A (More than 7), which implies an increase in alkalinity, contradicting standard agricultural chemistry principles regarding this fertilizer.
3846
Which of the following substances cannot be directly tested for pH using standard pH indicator paper?
pH paper works by changing color in response to the concentration of hydrogen ions in an aqueous solution. Because solid sodium bicarbonate is in a solid state, it lacks the necessary solvent medium (water) to allow for the ionization of ions required for the pH paper to function accurately. It must be dissolved in water first.
3847
In the context of universal indicators, how is a solution with a pH value between 4 and 5 classified?
The pH scale ranges from 0 to 14. A pH of 7 is neutral. Values below 7 indicate acidity, while values above 7 indicate alkalinity. A pH of 4 to 5 represents a moderate concentration of hydrogen ions, which is characteristic of a weak acid, as strong acids typically have pH values closer to 0 or 1.
3848
If a salt solution exhibits a pH of 14, what can be inferred about the nature of the acid and base from which it was derived?
A pH of 14 indicates a highly basic solution. A salt derived from a weak acid and a strong base undergoes anionic hydrolysis, resulting in a basic solution. While pH 14 is extremely high for most common salts, the logic follows that the basicity is driven by the strong base component.
3849
When 'Eno' salt (an antacid) is added to water, bubbles are released. Which gas is responsible for this effervescence?
Eno salt typically contains sodium bicarbonate and citric acid. When dissolved in water, these components react to undergo an acid-base neutralization, which releases carbon dioxide (CO2) gas as a byproduct, creating the characteristic bubbles.
3850
Which pH value represents the highest level of acidity in an aqueous solution?
The pH scale is logarithmic, where lower values indicate higher concentrations of hydrogen ions. A pH of 0 represents a very high concentration of H+ ions, making it more acidic than a solution with a pH of 1, 7, or 14.
