Question

Which of the following equations are correctly balanced?

A. \({ }_{p-5}^{q-1} X \longrightarrow{ }_{p-3}^{q-5} Y+{ }_{2}^{4} \mathrm{He}\)

B. \[\ {}^{q - 4}_{p - 4}Z \longrightarrow {}^{q - 4}_{p - 5}X + {}^{\phantom{-}0}_{-1}e \]

C. \({ }_{p-5}^{q-1} \mathrm{X} \longrightarrow{ }_{p-7}^{q-5} \mathrm{Y}+{ }_{2}^{4} \mathrm{He}\)

D. \[ {}^{q - 4}_{p - 7}Z \longrightarrow {}^{q - 4}_{p - 5}X + 2 \ {}^{\phantom{-}0}_{-1}e \]

Options

• Only D

• Only C

• Both A and B

• Both C and D

Answer 1

Both C and D

Explanation:

An equation is balanced when the mass numbers and the atomic numbers are equal on both sides.

A. Atomic number: \((p - 3) + 2 = p - 1 \neq p - 5\), so A is not balanced.

B. Atomic number: \((p - 5) + (-1) = p - 6 \neq p - 4\), so B is not balanced.

C. Mass number: \((q - 5) + 4 = q - 1\). Atomic number: \((p - 7) + 2 = p - 5\). So C is balanced.

D. Mass number: \((q - 4) + 0 = q - 4\). Atomic number: \((p - 5) + 2(-1) = p - 7\). So D is balanced.