Metals and Non-metals
NCERT Solution 1
Which of the following pairs will give displacement reactions?
- NaCl solution and copper metal
- MgCl2 solution and aluminium metal
- FeSO4 solution and silver metal
- AgNO3 solution and copper metal.
Answer: (d) AgNO3 solution and copper metal.
Which of the following methods is suitable for preventing an iron frying pan from rusting?
- Applying grease
- Applying paint
- Applying a coating of zinc
- All of the above.
Answer: (c) Applying a coating of zinc
An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be
Answer: (a) Calcium
Food cans are coated with tin and not with zinc because
- zinc is costlier than tin.
- zinc has a higher melting point than tin.
- zinc is more reactive than tin.
- zinc is less reactive than tin.
Answer: (c) zinc is more reactive than tin.
You are given a hammer, a battery, a bulb, wires and a switch.
- How could you use them to distinguish between samples of metals and non-metals?
Answer: If a substance can be beaten into thin sheets with the help of a hammer then the given substance is a metal. Otherwise, it is a non-metal. A circuit is made with the help of a battery, a bulb, wires and a switch. After that, the given substance is connected in the circuit. If the given substance ensures that the circuit is complete then it is a metal; else it is a non-metal.
- Assess the usefulness of these tests in distinguishing between metals and non-metals.
Answer: When a substance fulfills both the criteria then it can be confirmed as a metal. We know that some of the metals are brittle and graphite (a non-metal) is a good conductor of electricity. Hence, either of the tests cannot confirm a metal or non-metal; when the test is done in isolation.
What are amphoteric oxides? Give two examples of amphoteric oxides.
Answer: Some oxides show both acidic and basic characters. Such oxides are called amphoteric oxides. Amphoteric oxide reacts with acid as well as with base to form salt.
Example: Aluminium oxide and zinc oxide are examples of amphoteric oxide. When aluminium oxide reacts with a base, it gives salt and water.
Al2O3 + 2NaOH ⇨ 2NaAlO2 + H2O
When aluminium oxide reacts with an acid it gives salt and water.
Al2O3 + 6HCl ⇨ 2AlCl3 + 3H2O
Copyright © excellup 2014