VERY SHORT ANSWER-Class 10 – Science -Chemistry -Chapter 3 – Metals and Non-metals

VERY SHORT ANSWER-Class 10 – Science -Chemistry -Chapter 3 – Metals and Non-metals  

Q1) What is the difference between sodium atom and sodium ion?

Ans: When sodium atom loses 1 electron it changes into sodium ion. Differences between atom and ion are as follows:

Sodium Atom

1. Na has 11 electron in its shells

2. Na is neutral

Sodium Ion

Na⁺ has 10 electrons in its shell

Na⁺ is a positively charged ions

Q2. a) What are amphoteric oxides? Choose the amphoteric oxides from amongst the following:

 Na2O,  ZnO, Al2O3, CO2, H2O

b) Why is it that non metals do not displace hydrogen from dilute acid?

Ans. a) The oxides which are acidic as well as basic in nature are called amphoteric oxides. ZnO and Al2O3are amphoteric oxides.

b) Non metals can not loose electrons so that H+ ions become hydrogen gas.

 Q3. What is anodizing? What is its use?

Ans. The process of forming thick oxide layer of aluminium oxide that makes it resistant to further corrosion.

Q4. What is Aqua regia? What is its use?

Ans. It is a mixture of concentrated HCl and concentrated HNO3 in the ratio 3:1. It can dissolve gold and platinum.

Q5. why most of the metals do not occur as free elements

Most metals are not found in their free state because they are highly reactive and unstable. They react with other elements to form compounds to attain stability.

Q6. Define extraction?

Extraction is the process of obtaining pure metal from its ore. This process is also known as metallurgy. The process used to extract the ore depends on the nature of the ore and the impurities present in it.

Q7. NaCl does not conduct electricity in solid state whereas it does conduct electricity in solution as well as in molten state. Why?

Ans:

Because it is an ionic compound and does not contain free electrons in solid state.

Sodium chloride dissociates into ions in molten state or aqueous solutions. Hence they conduct electricity.

Q8.  Give reasons for the following observations:

(i) Highly reactive metals cannot be obtained from their oxides by heating

them with carbon.

(ii) Copper vessels get a green coat when left exposed to air in the rainy season.

Ans. (i) It is because these metals themselves are strong reducing agents. Therefore, cannot be reduced by reducing agent like carbon.

(ii) Copper vessels react with CO2, O2 and moisture to form green-coloured basic copper carbonate

[CuCO3.Cu(OH)2].

Q9. What is an alloy? State the constituents of solder. Which property of solder makes it suitable for welding electrical wires?

Answer. Alloy is a homogeneous mixture of two or more metals. One of them can be a non-metal also. Solder consists of lead and tin. It has low melting point which makes it suitable for welding electrical wires.

Q10. The way, metals like sodium, magnesium and iron react with air and water is an indication of their relative positions in the ‘reactivity series’. Is this statement true ? Justify your answer with examples.

Ans. Yes, sodium reacts explosively even with cold water, it is most reactive. Magnesium reacts with hot water, it is less reactive than Na. Iron reacts only with steam which shows it is least reactive among the three.

Q11. Why oxides of highly reactive metals cannot be reduced by carbon?

Ans :  It is because highly reactive metals themselves are good reducing agents, so they can’t be reduced by carbon.

Q12. Why does calcium float in water?

Ans :  Calcium form hydrogen gas on reaction with water, bubbles of hydrogen gas sticks to the calcium metal and that is why calcium floats in water. Ca(s) + 2H2 O(l)  $  Ca(OH)2 (aq) + H2 (g)

Q13 Why do silver ornaments lose their shine when kept in open air for sometime?

Ans : it is because Ag reacts with H2 S present in the atmosphere to form Ag2 S due to which it loses its shine.

Q14. Give reasons for the following:

a. Platinum, gold and silver are used for making jewellery.

b. Sodium, potassium and lithium are stored under kerosene oil.

c. Aluminium is highly reactive metal but still used for making cooking utensils. d. Carbonate and sulphide ores are usually converted into oxides during the process of extraction.

 Ans :   a. It is because they are lustrous metals.

b. These are highly reactive metals.

c. It forms an oxide layer on its surface which makes it passive.

d. It is easier to reduce a metal oxide than sulphides and carbonates.