Correct Answer: C. did not take God's message through Samuel seriously

Correct Answer: A) ascorbic acid and citric acid

Explanation

Ascorbic acid, also known as vitamin C, is a naturally occurring organic compound found in many fruits and vegetables, including citrus fruits. It is an essential nutrient for humans and plays a crucial role in various biological processes, such as collagen synthesis and the immune system's functioning.

Citric acid is another organic acid found in citrus fruits, such as lemons, oranges, and grapefruits. This weak acid contributes to the sour taste of these fruits and is also used as an additive in various food and beverage products to provide a sour or tart flavor.

Together, ascorbic acid and citric acid are responsible for the characteristic sour taste of citrus fruits, and they are the correct answer to this question.

Correct Answer: D. Anhydrous copper (II) tetraoxosulphate

Explanation

The question asks which of the given substances can be used to test for the presence of water in the laboratory. A substance used to test for water typically undergoes a distinct visual change (like a color change) when it comes into contact with water.

Let's examine each option:

• A. Anhydrous magnesium chloride (MgCl₂): While magnesium chloride is hygroscopic (absorbs moisture) and can form hydrates, it does not typically exhibit a distinct color change that serves as a clear visual test for water in the same way as indicator chemicals.

• B. Anhydrous calcium chloride (CaCl₂): Calcium chloride is an excellent desiccant (water-absorbing agent) and is often used to dry gases or maintain a dry environment. However, when it absorbs water, it primarily deliquesces (dissolves by absorbing moisture from the air) or forms a hydrate without a distinct color change. It mainly just gets wet or forms a solution.

• C. Anhydrous cobalt(II) chloride (CoCl₂): Anhydrous cobalt(II) chloride is blue. In the presence of water, it forms hydrated cobalt(II) chloride, which is pink. This distinct color change (blue to pink) makes it a reliable chemical test for water, often used in the form of cobalt chloride paper.

• D. Anhydrous copper(II) tetraoxosulphate (CuSO₄): Anhydrous copper(II) sulfate (tetraoxosulphate is the IUPAC name for sulfate) is white. In the presence of water, it forms hydrated copper(II) sulfate (specifically, the pentahydrate, CuSO₄·5H₂O), which is blue. This distinct color change (white to blue) makes it a very common and effective chemical test for the presence of water.

Both anhydrous cobalt(II) chloride and anhydrous copper(II) sulfate are widely used and accepted chemical tests for water due to their clear color changes. In many chemistry curricula, anhydrous copper(II) sulfate is prominently featured as a primary test for water.

Given that both C and D are valid tests, if only one option is to be selected, both are strong contenders. However, as the question asks Which of the following *can be used*, and both C and D indeed *can be used*, if forced to choose one, D is a very common and definitive example.

The final answer is D

Correct Answer: A. nitrogen fixation

Correct Answer: B. average age at which people die

Correct Answer: A. vibrissae

Correct Answer: A. there is little water vapour inthe air

Correct Answer: D. South-Atlantic

Correct Answer: B. no gills

Correct Answer: D. 79