Chemical Reactions and Classifications
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Chemical Reactions and Classifications
English 12 leveled MCQs Free
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7 marks Long answer
Classify the following as elements, compounds, or mixtures in Table 8.3. Carbon dioxide, sand, seawater, magnesium oxide, muddy water, aluminium, gold, oxygen, rust, iron sulfide, glucose, air, water, fruit juice, nitrogen, sodium chloride, sulfur, hydrogen, baking soda. Identify pure substances amongst these and list them below.
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Elements: Aluminium, Gold, Oxygen, Nitrogen, Sulfur; Compounds: Carbon dioxide, Magnesium oxide, Rust, Iron sulfide, Glucose, Water, Sodium chloride, Baking soda; Mixtures: Sand, Seawater, Muddy water, Air, Fruit juice.
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5 marks Long answer
Iron reacts with moist air to form iron oxide, and magnesium burns in oxygen to form magnesium oxide. Classify all the substances involved in the above reactions as elements, compounds or mixtures, with justification.
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Iron and magnesium are elements; iron oxide and magnesium oxide are compounds.
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5 marks Long answer
How would our daily lives be changed if water were not a compound but a mixture of hydrogen and oxygen?
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Daily life would be drastically different as hydrogen and oxygen gas are not stable together and would not provide the essential properties of water.
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4 marks Medium answer
In which of the following cases are all the examples correctly matched? Give reasons in support of your answers. (i) Elements — water, nitrogen, iron, air. (ii) Uniform mixtures— minerals, seawater, bronze, air. (iii) Pure substances— carbon dioxide, iron, oxygen, sugar. (iv) Non-uniform mixtures — air, sand, brass, muddy water.
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Only (iii) is correct; carbon dioxide, iron, oxygen, and sugar are pure substances.
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4 marks Medium answer
What new substance is formed when a mixture of iron filings and sulfur powder is heated, and how is it different from the original mixture? Also, write the word equation for the reaction.
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Iron sulfide is formed, which has different properties than the original mixture; word equation: Iron + Sulfur → Iron sulfide.
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4 marks Medium answer
Analyse Fig. 8.24. Identify Gas A. Also, write the word equation of the chemical reaction.
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Gas A is hydrogen; word equation: Iron + Hydrochloric acid → Iron chloride + Hydrogen.
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3 marks Medium answer
Water, a compound, has different properties compared to those of the elements oxygen and hydrogen from which it is formed. Justify this statement.
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Water exhibits properties distinct from oxygen and hydrogen due to the formation of new bonds in the compound.
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3 marks Medium answer
Is it possible for a substance to be classified as both an element and a compound? Explain why or why not.
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No, an element cannot be a compound as elements consist of one type of atom, while compounds consist of two or more different atoms.
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3 marks Medium answer
Write the names of any two compounds made only from non-metals, and also mention two uses of each of them.
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Examples: Carbon dioxide (used in carbonated drinks, as a refrigerant) and Glucose (used as an energy source in cells, in food products).
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2 marks Short answer
How can gold be classified as both a mineral and a metal?
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Gold is classified as a mineral due to its natural occurrence and as a metal due to its physical and chemical properties.
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1 marks Short answer
Consider the following reaction where two substances, A and B, combine to form a product C: $A + B \rightarrow C$. Assume that A and B cannot be broken down into simpler substances by chemical reactions. Based on this information, which of the following statements is correct? (i) A, B, and C are all compounds and only C has a fixed composition. (ii) C is a compound, and A and B have a fixed composition. (iii) A and B are compounds, and C has a fixed composition. (iv) A and B are elements, C is a compound, and has a fixed composition.
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A and B are elements, C is a compound, and has a fixed composition.
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1 marks Short answer
Assertion: Air is a mixture. Reason: A mixture is formed when two or more substances are mixed, without undergoing any chemical change. (i) Both Assertion and Reason are true and Reason is the correct explanation for Assertion. (ii) Both Assertion and Reason are true, but Reason is not the correct explanation for Assertion. (iii) Assertion is true, but Reason is false. (iv) Assertion is false, but Reason is true.
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Both Assertion and Reason are true and Reason is the correct explanation for Assertion.
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