Equivalent mass of Fe 0.9 O in reaction with acidic K 2 Cr 2 O 7 is : ( | TestHub

Passage / Comprehension

Equivalent Mass:

The equivalent mass of a substance is defined as the number of parts by mass of it which combine with or displace 1.0078 parts by mass of hydrogen, 8 parts by mass of oxygen, and 35.5 parts by mass of chlorine. The equivalent mass of a substance expressed in grams is called gram equivalent mass.

The equivalent mass of a substance is not constant; it depends upon the reaction in which the substance is participating. A compound may have different equivalent masses in different chemical reactions and under different experimental conditions.

(A) Equivalent mass of an acid:

It is the mass of an acid in grams which contains 1.0078 g of replaceable H⁺ ions, or it is the mass of acid which contains one mole of replaceable H⁺ ions. It may be calculated as:

$Eq u i v a l e n t ma sso f a c i d = \frac{M o l ec u l a r ma sso f a c i d}{B a s i c i t yo f a c i d}$

Basicity of acid = number of replaceable hydrogen atoms present in one molecule of acid.

(B) Equivalent mass of a base:

It is the mass of the base which contains one mole of replaceable OH⁻ ions in a molecule.

$Eq u i v a l e n t ma sso f ba se = \frac{M o l ec u l a r ma sso f ba se}{A c i d i t yo f ba se}$

Acidity of base = number of replaceable OH⁻ ions present in one molecule of the base.

Equivalent mass of an oxidizing agent:

(a) Electron concept:

$Eq u i v a l e n t ma sso f o x i d i z in g a g e n t = \frac{M o l ec u l a r ma sso f o x i d i z in g a g e n t}{N u mb ero f e l ec t ro n s g ain e d b yo n e m o l ec u l e}$

(b) Oxidation number concept:

$Eq u i v a l e n t ma sso f o x i d i z in g a g e n t = \frac{M o l ec u l a r ma sso f o x i d i z in g a g e n t}{T o t a l c han g e in o x i d a t i o nn u mb er p er m o l ec u l eo f o x i d i z in g a g e n t}$

Equivalent mass of $Fe_{0.9} O$ in reaction with acidic $K_{2} Cr_{2} O_{7}$ is : ( $M =$ Molar mass)

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Answer:

Solution:

Explain the question: Calculate the equivalent mass of non-stoichiometric Fe₀.₉₀O.

Concept: This question is based on the formula: Equivalent Weight = molar mass / change in total oxidation state.

Solution: Let the average oxidation state of Fe be $x$ . The oxidation state of O is -2.

$0.9 x + 1 (- 2) = 0$

$0.9 x = 2$

$x = \frac{2}{0.9} = \frac{20}{9}$

The final oxidation state of Fe is +3.

The change in oxidation state (ΔOS) per Fe atom is:

$Δ OS = F ina lOS - I ni t ia lOS = 3 - \frac{20}{9} = \frac{27 - 20}{9} = \frac{7}{9}$

The n-factor is given by:

$n - f a c t or = (m o l eso f F e) \times (Δ OSp er F e a t o m)$

$n - f a c t or = 0.9 \times \frac{7}{9} = \frac{9}{10} \times \frac{7}{9} = \frac{7}{10}$

The equivalent mass ( $E$ ) is:

$E = \frac{M o l a r ma ss ( M )}{n - f a c t or} = \frac{M}{\frac{7}{10}} = \frac{10 M}{7}$

Final Answer: The equivalent mass is $\frac{10 M}{7}$ .

Chemistry - Redox Reactions Question with Solution | TestHub

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