1.
What does this hazard symbol mean?
Correct Answer
A. Corrosive
Explanation
This hazard symbol indicates that the substance is corrosive. Corrosive substances can cause severe damage to skin, eyes, and other materials upon contact. They have the ability to eat away or destroy living tissue and can cause burns or other injuries.
2.
Which of these acids is most likely to be dangerous?
Correct Answer
C. Hydrochloric acid
Explanation
Hydrochloric acid is most likely to be dangerous because it is a strong acid that can cause severe burns and tissue damage upon contact. It is commonly used in laboratories and industrial settings, and even in small concentrations, it can be harmful to the skin, eyes, and respiratory system. Ingesting hydrochloric acid can also cause serious internal injuries and can be fatal. On the other hand, citric acid and carbonic acid are weak acids commonly found in food and beverages and are generally safe for consumption in normal quantities.
3.
What happens to litmus paper in acidic solutions?
Correct Answer
B. Blue litmus turns red
Explanation
In acidic solutions, the blue litmus paper turns red. This is because litmus paper is a pH indicator that changes color depending on the acidity or alkalinity of a solution. Blue litmus paper is blue in neutral or basic solutions, but when it comes into contact with an acidic solution, it turns red. This color change occurs due to a chemical reaction between the litmus paper and the acidic solution, indicating the presence of acidity.
4.
Universal indicator solution is usually green to begin with. What does this mean?
Correct Answer
C. It is neutral
Explanation
The fact that universal indicator solution is usually green to begin with suggests that it is neutral. Universal indicator is a mixture of several different indicators, and the green color indicates a pH level of around 7, which is considered neutral on the pH scale.
5.
A liquid has a pH of 7.5 - what does this mean?
Correct Answer
B. It is weakly alkaline
Explanation
A pH of 7.5 indicates that the liquid is weakly alkaline. pH is a measure of the acidity or alkalinity of a substance, with values below 7 indicating acidity, 7 indicating neutrality, and values above 7 indicating alkalinity. Therefore, a pH of 7.5 suggests that the liquid is slightly alkaline, but still closer to neutral than strongly alkaline.
6.
A liquid has a pH of 1 - what does this mean?
Correct Answer
B. It is strongly acidic
Explanation
A pH of 1 indicates a high concentration of hydrogen ions in the liquid, making it strongly acidic. Sodium hydroxide solution would have a pH greater than 7, indicating it is alkaline rather than acidic. Therefore, the correct answer is that the liquid is strongly acidic.
7.
What products are formed when a carbonate reacts with an acid?
Correct Answer
C. A salt, water and carbon dioxide
Explanation
When a carbonate reacts with an acid, it undergoes a chemical reaction called neutralization. In this reaction, the carbonate ion (CO3^2-) from the carbonate compound combines with the hydrogen ion (H+) from the acid to form water (H2O) and carbon dioxide (CO2). Additionally, the remaining ions from the acid and the carbonate form a salt. Therefore, the correct answer is that a carbonate reacts with an acid to form a salt, water, and carbon dioxide.
8.
What products are formed when a metal reacts with an acid?
Correct Answer
A. A salt and hydrogen
Explanation
When a metal reacts with an acid, the metal displaces hydrogen from the acid to form hydrogen gas. At the same time, the metal combines with the non-hydrogen part of the acid to form a salt. Therefore, the products formed when a metal reacts with an acid are a salt and hydrogen.
9.
Farmers use lime to neutralise their soils. What sort of substance is lime?
Correct Answer
A. A base
Explanation
Lime is a base because it is used by farmers to neutralize acidic soils. Bases are substances that have a high pH level and can react with acids to form a salt and water. Lime, also known as calcium oxide or calcium hydroxide, can increase the pH level of soil by neutralizing the acidity, making it more suitable for plant growth.
10.
Which gas is produced when magnesium reacts with hydrochloric acid?
Correct Answer
C. Hydrogen
Explanation
When magnesium reacts with hydrochloric acid, it undergoes a displacement reaction, where magnesium displaces hydrogen from the acid. This displacement reaction results in the production of hydrogen gas. Therefore, the correct answer is hydrogen.
11.
Which gas is produced when calcium carbonate reacts with hydrochloric acid?
Correct Answer
D. Carbon dioxide
Explanation
When calcium carbonate reacts with hydrochloric acid, it forms calcium chloride, water, and carbon dioxide. This is a classic example of a chemical reaction called a neutralization reaction. The carbon dioxide gas is produced as a result of the reaction between the calcium carbonate and the hydrochloric acid. Therefore, the correct answer is carbon dioxide.
12.
Which gas is produced when ammonium nitrate reacts with sodium hydroxide?
Correct Answer
C. Ammonia
Explanation
When ammonium nitrate reacts with sodium hydroxide, it produces ammonia gas. This reaction is known as a neutralization reaction, where the ammonium ion (NH4+) from ammonium nitrate reacts with the hydroxide ion (OH-) from sodium hydroxide to form ammonia gas (NH3), water (H2O), and sodium nitrate (NaNO3). Therefore, the correct answer is ammonia.
13.
Neutralisation is the process in which
Correct Answer
C. Acid react with alkali
Explanation
Neutralisation is a chemical reaction in which an acid reacts with an alkali to form a salt and water. This reaction occurs when the hydrogen ions (H+) from the acid combine with the hydroxide ions (OH-) from the alkali to form water (H2O). The remaining ions from the acid and alkali combine to form a salt. Therefore, the given answer "acid react with alkali" is correct.
14.
When unknown substance X react with acid, it release a gas which produces a "pop" sound with a burning splint. What type of substance does X belongs to?
Correct Answer
D. Metal
Explanation
The correct answer is metal because metals have the ability to react with acid to release hydrogen gas. This gas can ignite with a burning splint, producing a "pop" sound.
15.
When unknown substance Y react with acid, it release a gas which turns limewater chalky. What is the gas produced?
Correct Answer
D. Carbon dioxide
Explanation
When substance Y reacts with acid, it produces a gas that turns limewater chalky. This indicates the presence of carbon dioxide.