Question

if each purple sphere represents an atom of copper (cu), and each red sphere an atom of oxygen (o), how would you write a balanced equation demonstrates conservation of matter?
oa 2cu + 2o → cuo
ob 2cu + o₂ → 2cuo
oc cuo → 2cu + 2o
od 2cuo → 2cu + o₂

Explanation:

Step1: Count atoms on reactant side

• There are 2 Cu atoms (purple spheres) and 2 O atoms (red spheres in \(O_2\) molecule).

Step2: Count atoms on product side

• In option B, for \(2CuO\), there are \(2\times1 = 2\) Cu atoms and \(2\times1= 2\) O atoms.
• Option A: Reactant side has 2 Cu and 2 O, product side has 1 Cu and 1 O (unbalanced).
• Option C: Product side has 2 Cu and 2 O, reactant side has 1 Cu and 1 O (unbalanced, also wrong direction as per the diagram which is a synthesis reaction not decomposition).
• Option D: Reactant side has 2 Cu and 2 O (in \(2CuO\)), product side has 2 Cu and 2 O (in \(O_2\)), but the diagram shows synthesis (reactants \(Cu\) and \(O_2\) forming \(CuO\)) not decomposition (wrong direction).

Answer:

B. \(2Cu + O_2
ightarrow2CuO\)