Question

In the balanced equations, the values of \(a\), \(b\) and \(c\) are respectively
\[ aFe_3O_4(s)+bAl(s)\longrightarrow Fe(s)+Al_2O_3(s) \] \[ V_2O_5(s)+cCa(s)\longrightarrow V(s)+CaO(s) \]

• A. \(4,5,5\)
• B. \(3,4,5\)
• C. \(3,8,5\)
• D. \(4,8,5\)

Hint:

While balancing chemical equations, first balance atoms that appear in complex compounds, then balance metals, and finally check oxygen atoms.

Answer 1

The Correct Option is C

Step 1: Balancing the first reaction.
a Fe₃O₄ + b Al → Fe + Al₂O₃. Using 3 Fe₃O₄ gives 12 oxygen atoms. To balance, 4 Al₂O₃ are needed (4 × 3 = 12 O). This provides 8 Al atoms, so b = 8. Also, 3 Fe₃O₄ supplies 9 Fe atoms. Balanced: 3 Fe₃O₄ + 8 Al → 9 Fe + 4 Al₂O₃, hence a = 3, b = 8.

Step 2: Balancing the second reaction.
V₂O₅ + c Ca → V + CaO. V₂O₅ contains 5 oxygen atoms; each CaO has 1 oxygen, so 5 CaO and 5 Ca are required, giving c = 5. Balanced: V₂O₅ + 5 Ca → 2 V + 5 CaO.

Step 3: Consolidating the values.
From the first: a = 3, b = 8. From the second: c = 5. Thus a, b, c = 3, 8, 5.

Step 4: Final answer.
Therefore, the required coefficients are 3, 8, 5.