Question

Methane is a major component of purified natural gas used for heating and cooking. When 1 mole of methane gas burns with oxygen to produce carbon dioxide and water, 883 kJ is produced. Methane gas has a density of 0.715 g/L at STP. For transport, the natural gas is cooled to -163 ∘C to form liquefied natural gas (LNG) with a density of 0.45 g/mL. A tank on a ship can hold 7.0 million gallons of LNG.

A. Draw the electron-dot formula of methane, which has the formula CH4. Draw the Lewis dot structure for CH4.

B. What is the mass, in kilograms, of LNG (assume that LNG is all methane) transported in one tank on a ship?

C. What is the volume, in liters, of LNG (methane) from one tank when the LNG is converted to gas at STP?

D. Write the balanced equation for the combustion of methane in a gas burner. Express your answer as a chemical equation. Identify all of the phases in your answer.

E. How many kilograms of oxygen are needed to react with all of the methane provided by one tank of LNG?

F. How much heat, in kilojoules, is released from burning all of the methane in one tank of LNG?

Answer 1

Answer.

Given that,

molar mass of methane(M) = 16 g/mol

density of methane (d) = 0.715 g/L

density of LNG (D) = 0.45 g/mL = 450 g/L

temperature (T) = -163 + 273 = 110 K

pressure (p) = 1 atm

R = 0.08205 L-atm/mol-K

volume of ship (V) = 7 million gallon = 7*10⁶ gallon =2.65*10⁷ L (since 1 gallon = 3.785 L)

A.

Left side = Lewid dot structures

Right side = Electron dot structure

B. mass of LNG = density*volume = D*V = 450 g/L * 2.65*10⁷ L = 1.1925*10¹⁰ g
mass of methane = 1.1925*10⁷ kg

C. Using ideal gas equation pv = nRT, we have

moles of methane = mass/molar mass = 1.1925*10¹⁰ g / 16 g/mol = 7.45*10⁸ moles

Therefore,

v = 7.45*10⁸*(0.08205)*110/1 = 6.72*10⁹ L

D. The balanced equation for combustion of methane is

E. 1 mole of methane requires 2 moles of oxygen. Therefore,

7.45*10⁸ moles will require = 2*7.45*10⁸ moles = 1.49*10⁹ moles of O₂.

F. 1 mole of methane burning gives of energy.

Therefore,

7.45*10⁸ moles will release = 7.45*10⁸*883 = 6.578*10¹¹ kJ of energy.