Question

1 arrange the metal al, cu, fe, pb, mg, zn, and na in descending order of their reactivity towards
2 give names of two metals that can displace hydrogen from dilute acid and two metals that cannot do so
3 give two examples of metals that -1 can be cut with a knife easily 2 are the best conductor of heat

Answer 1

Answer:

(a) Na ,Mg , Al , Zn ,Fe , Pb , Cu

(b) zinc and iron can displace hydrogen but copper and mercury do not

(c) 1 sodium

2 silver

Answer 2

Answer 1.

Decreasing reactivity order of metals :- Na > Mg > Al > Zn > Fe > Pb > Cu.

Because reactivity order decreases from left to right and top to bottom in periodic table.  Cu, Au and Ag are less reactive. So, they are kept at the bottom.

$\rule{100}2$

Answer 2.

Zinc and Iron are the metals that can displace hydrogen from dilute acid.

$\sf{Zn\: + \:2HCl}$ → $\sf{ZnCl_2 \:+ \:H_2}$

$\sf{Fe\: +\: 2HCl}$ → $\sf{FeCl_2\: + \:H_2}$

On the other hand; Platinium and Gold are the metals that can't displace hydrogen from dilute acid.

Because both Zn and Fe are more reactive than H (hydrogen) due to this they displace hydrogen from it's position.

(When more reactive element displaces less reactive element from it's position it is known as Displacement reaction.)

$\rule{100}2$

Answer 3.

Sodium and Potassium are soft metals that can be easily cut with knife.

As both of these are alkali metals. Due to this they have my one valence electron in their orbitals. Also their atomic size is large, due to this they have more space between their atoms.

Because of large space; weak metallic bond will formed. Due to this we can easily break them in our hands.