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Which statement regarding metal and non-metal oxides is not true?

A. Metal oxides are bases and forms alkalis in water.

B. Non-metal oxides form acids in water.

C. Solutions of non-metal oxides change red litmus blue.

D. Metal oxides color universal indicator blue and non-metal oxides color it red.

Answer Explanation:

A. Metal oxides are bases and form alkalis in water: This statement is generally true. Metal oxides typically react with water to form basic solutions (alkalis). Therefore, this statement is true.

B. Non-metal oxides form acids in water: This statement is generally true. Non-metal oxides typically react with water to form acidic solutions. Therefore, this statement is true.

C. Solutions of non-metal oxides change red litmus blue: This statement is not true. Non-metal oxides typically form acidic solutions in water, which would not change red litmus paper to blue. Instead, they would typically turn blue litmus paper red.

D. Metal oxides color universal indicator blue and non-metal oxides color it red: This statement is generally true. Metal oxides tend to produce basic solutions, which turn universal indicator blue. Non-metal oxides tend to produce acidic solutions, which turn universal indicator red. Therefore, this statement is true.

Therefore, the Correct Answer is C.

Q #1: Which type of solution is one with a pH of 8?:

A. Acidic

B. Basic

C. Neutral

D. Pure

Answer Explanation

a. Acidic: Solutions with pH values below 7 are considered acidic. A pH of 8 indicates a solution that is more basic than acidic.

b. Basic (Correct Answer): Solutions with pH values above 7 are considered basic or alkaline. A pH of 8 indicates a basic solution.

c. Neutral: Solutions with a pH of 7 are considered neutral. A pH of 8 indicates a solution that is slightly basic, not neutral.
Q #2: How would you remove unreacted copper oxide from solution?

A. Filtration

B. Distillation

C. Evaporation

D. Decantation

Answer Explanation

A) Filtration (Correct Answer): Filtration is a commonly used method to separate solid particles, such as unreacted copper oxide, from a liquid solution. The solution containing the dissolved copper sulfate can pass through the filter paper, while the solid copper oxide particles are retained on the filter.

B) Distillation: Distillation is a process used to separate components of a mixture based on differences in their boiling points. It is not typically used to separate solid particles from a liquid solution.

C) Evaporation: Evaporation involves heating the solution to allow the solvent (water) to vaporize, leaving behind the solute (copper sulfate) as solid crystals. While evaporation can concentrate the solution, it does not effectively remove solid particles like unreacted copper oxide.

D) Decantation: Decantation involves pouring off the liquid portion of a mixture, leaving the solid behind. While it can be used to separate solid and liquid phases, it may not effectively separate fine solid particles like unreacted copper oxide from the solution. Filtration would be a more suitable method for this purpose.
Q #3: Why do farmers use ammonium salts on their fields?

A. To prevent soil erosion

B. To increase soil acidity

C. To help plants grow (as fertilizers)

D. To reduce soil salinity

Answer Explanation

A) To prevent soil erosion: While certain soil management practices may involve measures to prevent erosion, the use of ammonium salts specifically does not directly relate to preventing soil erosion.

B) To increase soil acidity: Ammonium salts, such as ammonium sulfate, can actually decrease soil pH, making the soil more acidic. However, this is not typically the primary reason farmers use these salts.

C) To help plants grow (as fertilizers) (Correct Answer): Ammonium salts are commonly used as fertilizers because they provide essential nitrogen to plants in a form that they can readily absorb. Nitrogen is a crucial nutrient for plant growth, and ammonium salts serve as a source of nitrogen for crops.

D) To reduce soil salinity: Ammonium salts are not typically used to reduce soil salinity. Salinity issues in soil are typically addressed through other methods such as leaching or soil amendments, rather than the addition of ammonium salts.

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