Understanding Equivalent Weight
Equivalent weight is a fundamental concept in chemistry, representing the mass of an element or compound that reacts with or replaces a fixed quantity of a standard (like 1 gram of hydrogen or 8 grams of oxygen).
The formula for the equivalent weight of an element is:
$$Equivalent \; Weight = \frac{Atomic \; Weight}{Valency}$$
Step-by-Step Solutions
i. Fe in $Fe_2O_3$
- The valency of O is 2. In $Fe_2O_3$, total negative charge = $3 \times 2 = 6$. Therefore, $2 \times \text{Valency of Fe} = 6$, so $\text{Valency of Fe} = 3$.
- Given: Atomic weight of Fe = 56.
- $Equivalent \; Weight = \frac{56}{3} = 18.67$.
ii. Mg in $MgCl_2$
- Chlorine (Cl) has a valency of 1. Since there are two Cl atoms, the valency of Mg is 2.
- Atomic weight of Mg = 24.3.
- $Equivalent \; Weight = \frac{24.3}{2} = 12.15$.
iii. C in $CH_4$
- Hydrogen has a valency of 1. In $CH_4$, there are 4 H atoms, so C has a valency of 4.
- Atomic weight of C = 12.
- $Equivalent \; Weight = \frac{12}{4} = 3$.
iv. N in $NH_3$
- In $NH_3$, 3 H atoms are attached to 1 N atom, so N has a valency of 3.
- Atomic weight of N = 14.
- $Equivalent \; Weight = \frac{14}{3} = 4.67$.