chemistry unit 8

Question 1

(mol-mol conversions) How many moles of carbon dioxide will form from 5 moles of oxygen gas and excess methane? CH₄ + 2O₂ → CO₂ + 2H₂O

Answer 1

From this equation, we can see that 1 mole of methane (CH₄) reacts with 2 moles of oxygen gas (O₂) to produce 1 mole of carbon dioxide (CO₂). So for every 2 O₂, there’s 1 CH₄, therefore 5 O₂ is 2.5 CH₄.

Question 2

(mol->mass conversions) 45.0 grams of ZnO to moles of O₂.
2ZnS + 3O₂ →2ZnO + 2SO₂

Answer 2

first find ZnO weight (81.38), then divide it by 45 to get .553 moles. 2 zinc oxide for every 3 O₂, so 2/3 x .553 = .369 moles.

Question 3

(mass->mass) How many grams of C₂H₆ will be produced from 50.0 grams of CO₂ and excess O₂? 2C₂H₆ + 7O₂ →2CO₂ + 6H₂O

Answer 3

From the equation, we can see that 2 moles of C₂H₆ produces 2 moles of CO₂. Molar mass of CO₂ is 44.01, so 50/44.01 = 1.136 moles CO₂. Now, 1.136 x molar mass of C₂H₆ (30.07) = 34.18g.

Question 4

(limiting reactant) 75.0 grams of silicon dioxide reacts with 30.0 grams of carbon. How many grams of carbon monoxide can be
produced? SiO₂ + 2C → 2CO + Si

Answer 4

SiO₂ molar mass = 60.09. C molar mass = 12.01. SiO₂ 75/60.09 = 1.248 mol. C 30/12.01 = 2.498 mol.