Give reasons for the following :
1)carbon can reduce zinc oxide to zinc but not calcium oxide to calcium.
2.) copper and aluminum wires are usually used for electricity transmission.
3.)alloys are used in electrical heating devices rather than pure metals.
4.)gold ornaments look new even after several years of use.
Answers
Answer:
1.Yes, carbon can reduce zinc oxide to zinc but carbon can not reduce calcium oxide to calcium because carbon is more reactive than zinc but Calcium is more reactive than carbon so carbon can not displace calcium. ... Thus its reactivity is very less and very much reluctant to form compound.
2.Copper and aluminium wires are usually used for electricity transmission because Copper and Alluminium are -good conductors of electricity, cheap and are easily available. Other good conductors like silver and gold metal can also be used for electricity transmission but they are costly and are not abundant in the atmosphere.
3.Alloys are used for making electrical heating devices due to the following reasons; i) They have a higher resistivity as compared to pure metals. ii) They do not burn in oxygen i.e. they don’t oxidize readily at high temperatures.
4.As we see the reactivity series, gold is situated at the bottom. Thus its reactivity is very less and very much reluctant to form compound. For this nature gold is also called noble metal. Thats why gold exists in pure state and looks like new.
5.Iron when exposed to moist air for a long time acquires a coating of a brown flaky substance called rust. Rust can eat up the metal, thus paint is applied on the iron to prevent its contact with oxygen present in the air.
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