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Class 10, Science, Chapter-3, Lecture-2, Reactivity Series of Metals (Notes)

 

(continued from the previous page)

 

5. Reaction with Acids:

Metals react with non-oxidizing dilute acids to produce salts and liberate Hydrogen Gas

$$2Na\,\,\,\,\,\,\,\,\, + \,\,\,\,\,\,2\;HCl\;\;\;\;\buildrel {\,\,\,\,\,\,\,\,\,\,\,\,\;\;} \over
 \longrightarrow \;\;2\;NaCl\;\;\;\; + \;\;\;{H_2}$$

$$2Al\,\,\,\,\,\,\,\,\, + \,\,\,\,\,\,3\;{H_2}S{O_4}\;\;\;\;\buildrel {\,\,\,\,\,\,\,\,\,\,\,\,\;\;} \over
 \longrightarrow \;\;A{l_2}{(S{O_4})_3}\;\;\;\; + \;\;\;3{H_2}$$

$$Cu\,\,\,\,\,\,\,\,\, + \,\,\,\,\,\,HCl\;\;\;\;\buildrel {\,\,\,\,\,\,\,\,\,\,\,\,\;\;} \over
 \longrightarrow \;\;\;No\;{\mathop{\rm Re}\nolimits} action$$

Metals do not liberate Hydrogen with dilute Nitric Acid:

Reason

Dilute HNO3 is an oxidising agent, and it oxidises the hydrogen gas to H2O.

Metals Can Displace Hydrogen from Acids But Non-Metals Cannot

Reason

Non-oxidizing dilute acids contain removable hydrogen ions.

Metals being electropositive in nature supply electrons to the hydrogen ions and convert them into hydrogen atoms.

Non-metals being electronegative in nature, cannot supply electrons.

6. Reaction with Chlorine:

Metals react with chlorine to form electrovalent chlorides (by transfer of electrons)

$$2\;Na\;\; + \;\;C{l_2}\;\;\buildrel {} \over
 \longrightarrow \;\;2\;NaCl$$

$$2\;Fe\;\; + \;\;3\;C{l_2}\;\;\buildrel {} \over
 \longrightarrow \;\;2\;FeC{l_3}$$

 

Non-metals react with chlorine to form covalent chlorides

$${H_2}\;\; + \;\;C{l_2}\;\;\;\;\;\buildrel {\;\;\;\;\;\;\,\;\;\;\;} \over
 \longrightarrow \;\;2\;HCl$$

$$Si\;\;\; + \;\;2\;C{l_2}\;\;\buildrel {\;\;\;\;\;\;\;\;\;\;\;} \over
 \longrightarrow \;\;SiC{l_4}$$

 

7.Reaction with Hydrogen:

Few highly reactive metals (K, Na, Ca, Mg) force the hydrogen atom to accept electrons and form salts called HYDRIDES which are electrovalent.

$${\rm{2 K (s)}}\;\;{\rm{    + }}\;\;{{\rm{H}}_{\rm{2}}}{\rm{ (g)}}\;\;\;\buildrel {\;\;\;\;\;\;\,\;\;\;\;} \over
 \longrightarrow \;\;{\rm{2}}\;{\rm{KH (s)}}$$

$${\rm{2 Na (s)}}\;\;\;{\rm{ + }}\;\;{{\rm{H}}_{\rm{2}}}{\rm{ (g) }}\;\;\buildrel {\;\;\;\;\;\;\;\;\;\;\;} \over
 \longrightarrow \;\;{\rm{2 NaH (s)}}$$

 Non-metals react with Hydrogen to form covalent Hydrides.

$$2{H_2}\;\; + \;\;{O_2}\;\;\;\;\;\buildrel {\;\;\;\;\;\;\,\;\;\;\;} \over
 \longrightarrow \;\;2\;{H_2}O$$

$${N_2}\;\;\; + \;\;3\;{H_2}\;\;\buildrel {\;\;\;\;\;\;\;\;\;\;\;} \over
 \longrightarrow \;\;2\;N{H_3}$$

  DIFFERENCES BETWEEN :

METALS

NON-METALS

1. Have 1, 2 or 3 electrons in the outermost shell1. Have 4 – 8 electrons in the outermost shell
2. are electropositive elements2. are electronegative elements
3. act as a reducing agent.3. act as an oxidizing agent.
4. form basic oxides4. form acidic or neutral oxides
5. replace hydrogen from acids and form salts5. do not replace hydrogen from acids
6. react with chlorine to form electrovalent chlorides6. react with chlorine to form covalent chlorides
7. react with hydrogen to form electrovalent hydrides7. react with hydrogen to form covalent hydrides

REACTIVITY SERIES OF METALS :

The arrangement of metals in order of decreasing reactivity is called the reactivity series of metals.

K, Na, Ba, Ca, Mg, Al, Zn, Fe, Ni, Sn, Pb, H, Cu, Hg, Ag, Au, Pt

Blue Colour of Copper Sulphate Solution Is Destroyed When Iron Filings Are Added to It.

Reason —

Copper sulphate is blue due to the presence of copper ions.

When iron filings are added to the copper sulphate solution, iron displaces copper and iron sulphate is formed because iron (Fe) is more reactive than copper (Cu).

$$CuS{O_4}\left( {aq} \right)\;\; + \;\;Fe\left( s \right)\;\;\;\;\;\buildrel {\;\;\;\;\;\;\,\;\;\;\;} \over
 \longrightarrow \;\;FeS{O_4}\left( {aq} \right) + Cu\left( s \right)$$

Copper ions accept electrons and become copper atoms.

So, the blue colour is destroyed due to the conversion of copper sulphate into iron sulphate.