Answer:
CH₄ is the excess reagent and SO₄²⁻ is the limiting reagent.
0.040 g
Explanation:
Step 1: Write the balanced reaction for the methane anaerobic oxidation
CH₄ + SO₄²⁻ ⇒ S²⁻ + CO₂ + 2 H₂O
Step 2: Establish the theoretical mass ratio between the reactants
According to the balanced equation, the theoretical mass ratio of CH₄ to SO₄²⁻ is 16.04:96.06 = 0.1670:1
Step 3: Establish the experimental mass ratio between the reactants
50 mg (0.050 g) of CH₄ react with 60 mg (0.060 g) of SO₄²⁻. The experimental mass ratio of CH₄ to SO₄²⁻ is 0.050:0.060 = 0.83:1
Comparing both mass ratios, we can deduce that CH₄ is the excess reagent and SO₄²⁻ is the limiting reagent.
Step 4: Calculate the mass excess of CH₄
The mass of CH₄ that reacts with 0.060 g of SO₄²⁻ is:
0.060 g SO₄²⁻ 16.04 g CH₄/96.06 g SO₄²⁻ = 0.010 g CH₄
The mass excess of CH₄ is:
0.050 g - 0.010 g = 0.040 g
