Question

Suppose a boil water notice is sent out advising all residents in the area to boil their water before drinking it or using it for cooking. You need to boil 18.0 L of water using your natrual gas (primarily methane) stove. What volume of natural gas is needed to boil the water if only 10.4% of the heat generated goes towards heating the water. Assume the density of methane is 0.660g/L, the density of water is 1.00 g/mL and that the water has an initial temperature of 23.2 °C. Enthalpy of formation values can be found in this table. Assume that gascous water is formed in the combustion of methane. volume of methane:

Answer 1

CH₄ (g) + 2 O₂ (g) ==> CO₂ (g) + 2 H₂O (l) ; initially water in liquid state only, but later due to high temperature it is gaseous

∆H⁰_rxn = [-393.5 + (2 x -285.80] - [-74.6 + (2 x 0)] = -890.5 kJ/mol

amount of heat required to heat 18000 g of water from 23.2 ⁰C to 100 ⁰C

Q = m x Cs x ΔT

m = mass; Cs = specific heat: ΔT = temp. difference; Q = Heat absorbed or Released.

To heat the water from 23.2 °C to boiling at 100°C

= 18000 g x 4.184 J/g/°C x 76.8°C = 5783.9616 kJ

To vaporize the water to steam (gaseous) at 100°C

= 18000 g x 2,260 J/g = 40680000 J = 40680 kJ.

Total heat = 5783.9616 kJ + 40680 kJ = 46463.9616 kJ

but efficiency = 10.4 %

heat required will be = 46463.9616 kJ / 10.4% = 446768.861538 kJ required

mol methane required = 446768.861538 / 890.5 kJ/mol = 502 501.70562778 mol

mass of methane = 501.70562778 mol x 16.04 g/mol = 8047.3582696 g

volume = 8047.3582696 g / 0.660 g/L = 12192.9670751 L

volume of methane = 12193 L

20 Suppose a boil water notice is sent out advising all residents in the area to boil their water hefore drinking it or using it for cooking. You need to boil 18.0 L of water using your natrual gas (primarily methane) stove. What volume of natural gas is needed to boil the water if only 10.4% of the heat generated goes towards heating the water. Assume the density of methane is 0.660g/L. the density of water is 1.00 g/ml., and that the water has an initial temperature of 23.2 °C. Enthalpy of formation values can be found in this table. Assume that gaseous water is formed in the combustion of methane volume of methane:12193 L

Hope this helped you!

Thank You So Much! Please Rate this answer as you wish.("Thumbs Up")