Question

how does the law of conservation of mass apply to this reaction: c₂h₄ + o₂ → h₂o + co₂?
the law of conservation of mass has already been applied. there is an equal number of each element on both sides of the equation.
each element needs to be balanced.
only the oxygen needs to be balanced. there are equal numbers of hydrogen and carbon
the equation needs to be balanced. there are fewer oxygen atoms in the equation than hydrogen or carbon.

Explanation:

Step1: Count atoms on both sides

For \(C_2H_4 + O_2
ightarrow H_2O+CO_2\), on the left side: \(C = 2\), \(H = 4\), \(O=2\). On the right side: \(C = 1\), \(H = 2\), \(O = 3\).

Step2: Analyze options

• Option A: Incorrect, as atoms are not balanced initially.
• Option B: Correct, as all elements (\(C\), \(H\), \(O\)) need balancing.
• Option C: Incorrect, \(C\) and \(H\) also need balancing.
• Option D: Incorrect, it's about balancing all elements, not just comparing oxygen to \(H\) or \(C\).

Answer:

B. Each element needs to be balanced.