Question

The correct order of acidic strength is:
A. $C{l_2}{O_7} > S{O_3} > {P_4}{O_{10}}$
B. $C{O_2} > {N_2}{O_5} > S{O_3}$
C. $N{a_2}O > MgO > A{l_2}{O_3}$
D. ${K_2}O > CaO > MgO$

Answer 1

The acidic strength of an acid is defined as the tendency of the acid to dissociate into its corresponding ions in order to release a proton and the anion. The acidic strength of a strong acid is high and that of a weak acid is low. This means that on dissociation, a strong acid releases its proton at a much faster rate than the weak acid.

Complete step by step answer:
The factors on which the strength of an acid depends on are as follows:
(i) Electronegativity: The higher the value of the electronegativity of the central atom, the greater will be the acidic strength. This means that the central atom should have a high tendency to accept a shared pair of electrons towards itself and the acid should retain the negative charge and form a stable anion.
(ii) Oxidation number: The greater the oxidation number of the central atom of the oxide, the greater the acidic strength will be.
In a periodic table, the acidic strength of an atom increases across a period and decreases down the group. In the above options, the correct order of acidic strength of the oxides is:
$C{l_2}{O_7} > S{O_3} > {P_4}{O_{10}}$
The oxidation state of the oxides is as follows:
Let the oxidation number of the chlorine atom be $'x'$ .
$C{l_2}{O_7} = 2x + 7( - 2) \Rightarrow x = + 7$
Let the oxidation number of the sulfur atom be $'y'$ .
$S{O_3} = y + 3( - 2) \Rightarrow y = + 6$
Let the oxidation number of the phosphorus atom be $'z'$ .
${P_4}{O_{10}} = 4z + 10( - 2) \Rightarrow z = + 5$
Thus, as we can see that the order of oxidation is in a decreasing manner, this means that this option is correct.

So, the correct answer is Option A .

Note:
An acid having a greater degree of dissociation behaves as a stronger acid. The degree of dissociation of an acid depends on the following two factors.
(i) Strength of $H - A$bond
(ii) Polarity of $H - A$ bond
Here, $A$ is the acidic anion.