Question 1

Copper is extracted from its ore by reduction with carbon monoxide in a blast furnace. Which of the following best describes why copper cannot be extracted by direct reduction with carbon at high temperature in the same way as iron?

Accepted Answer

Copper is less reactive than carbon in the reactivity series of metals. According to the NCERT Class 10 Chemistry principle, a metal can only be displaced from its ore by a reducing agent (non-metal or another metal) that is more reactive than the metal itself. Since carbon is more reactive than copper, carbon can reduce copper oxide (CuO) to copper metal. However, the question tests understanding of the reactivity series: copper sits below carbon in the series, meaning carbon IS more reactive and CAN reduce copper. The correct answer is that copper IS extracted using carbon monoxide (a reducing agent more effective than solid carbon at lower temperatures in industrial practice), but the fundamental principle is that carbon/carbon monoxide (being more reactive than copper) can reduce copper oxide. Option B correctly identifies that copper CAN be reduced by carbon because carbon is more reactive than copper in the reactivity series. Option A incorrectly reverses the reactivity relationship. Option C confuses the extraction method with the thermodynamic feasibility. Option D misapplies the concept of noble metals. Therefore, answer is B.

Question 2

Copper is extracted from its ore by reduction with carbon monoxide in a blast furnace. Which of the following statements correctly describes why copper cannot be extracted by direct reduction with carbon at high temperature in the same manner as iron?

Accepted Answer

According to the reactivity series and principles of metal extraction taught in NCERT Class 10, a metal can be extracted from its oxide by reduction with a non-metal only if that non-metal is more reactive than the metal being extracted. Iron is less reactive than carbon, so carbon can reduce iron oxide (Fe₂O₃) to iron. However, copper is MORE reactive than carbon in the reactivity series. Therefore, carbon cannot reduce copper oxide (CuO) to copper — instead, copper would reduce any carbon monoxide formed back to carbon, making the process thermodynamically unfavorable. Copper is extracted using carbon monoxide (a stronger reducing agent than carbon) or by electrolytic refining after initial smelting. Option B correctly identifies that copper is more reactive than carbon and thus cannot be reduced by direct carbon reduction. Option A incorrectly reverses the reactivity relationship. Option C confuses the extraction method (electrolysis is used for refining, not primary extraction from ore). Option D misapplies the concept — carbon CAN reduce less reactive metals like iron, but NOT more reactive ones like copper.

Question 3

The process of coating a metal with a layer of zinc to prevent corrosion is called:

Accepted Answer

Galvanization is the electrochemical process of coating steel or iron with a layer of zinc (Zn) to protect it from rusting. The zinc layer acts as a barrier and also as a sacrificial anode, corroding preferentially to the underlying iron. This is a standard corrosion prevention method covered in NCERT Class 10.

Question 4

Stainless steel is an alloy that resists corrosion. Which of the following is the correct composition of stainless steel?

Accepted Answer

Stainless steel is primarily an alloy of iron (Fe) with chromium (Cr, typically 10–30%) and nickel (Ni, typically 8–12%), along with small amounts of carbon. The chromium forms a thin, protective oxide layer (Cr₂O₃) on the surface that prevents corrosion. This composition is standard in NCERT Class 10 Chemistry.

Question 5

When a metal reacts with dilute hydrochloric acid, hydrogen gas is evolved. Which of the following metals will NOT produce hydrogen gas when reacted with dilute HCl?

Accepted Answer

Copper is below hydrogen in the reactivity series, so it cannot displace hydrogen from dilute acids. Only metals above hydrogen in the reactivity series (such as zinc, iron, magnesium) can displace hydrogen and produce H₂ gas. Copper reacts with concentrated nitric acid but not with dilute HCl.

Question 6

An alloy of copper and tin is used in making bells and statues. This alloy is called:

Accepted Answer

Bronze is the alloy formed by mixing copper (88–90%) and tin (10–12%). It is harder and more brittle than pure copper, making it ideal for casting bells and statues. Brass (Cu + Zn) is used for decorative items and musical instruments. Solder (Pb + Sn) is used for joining metals. Steel (Fe + C) is used for structural purposes.

Question 7

Which of the following metals is most resistant to corrosion and does NOT require protective coating in normal atmospheric conditions?

Accepted Answer

Gold is a noble metal with extremely high resistance to corrosion due to its position at the bottom of the reactivity series. It does not oxidize or react with oxygen, water, or common acids under normal conditions. Iron and copper require protective coatings (paint, galvanization, or patina management) to prevent rust and corrosion respectively.

Question 8

When zinc metal is added to dilute sulfuric acid, hydrogen gas is evolved. However, when copper metal is added to the same dilute sulfuric acid under identical conditions, no hydrogen gas is evolved. Which of the following correctly explains this observation based on the reactivity series?

Accepted Answer

This question tests understanding of the reactivity series and its relationship to metal displacement reactions. According to the reactivity series (NCERT Class 10), zinc is more reactive than hydrogen, while copper is less reactive than hydrogen. In a displacement reaction, a more reactive element can displace a less reactive element from its compound. Since zinc is above hydrogen in the reactivity series, zinc can displace hydrogen from H₂SO₄, producing H₂ gas. Conversely, copper is below hydrogen in the reactivity series, so it cannot displace hydrogen from the acid. Therefore, no reaction occurs with copper. The reactivity series order relevant here is: Zn > H > Cu. This is a fundamental principle tested in Class 10 chemistry. Option B correctly identifies that zinc is more reactive than hydrogen (and thus can displace it), while copper is less reactive than hydrogen (and thus cannot displace it). Option A incorrectly suggests both metals have similar reactivity. Option C confuses the concept by suggesting copper's inertness is due to its density rather than its position in the reactivity series. Option D reverses the reactivity order, which is a common misconception among students who confuse reactivity with electrical conductivity or malleability.

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