Answer:
a) 0.115 g
Explanation:
The balanced reaction is:
CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)
To heat 55g of water, the energy in form of heat necessary can be calculated by:
Q = mcΔT
where Q is the heat, m is the mass, c is the specific heat (for water, c = 4.18 J/gºC), and ΔT is the variation of the temperature, which is 25ºC, so:
Q = 55x4.18x25
Q = 5747.5 J = 5.7475 kJ
So, for the reaction, 1 mol of CH₄ releases 802.3 kJ, so to release 5.7475 kJ will be necessary:
1 mol ---------------- 802.3 kJ
x ---------------- 5.7475 kJ
By a simple direct three rule:
802.3x = 5.7475
x = 7.164x10⁻³mol
The molar mass of CH₄ is : 12 (of C) + 4x1 (of H) = 16 g/mol
The mass is equal to the number of moles multiplied by molar mass, the:
m = 7.164x10⁻³x16
m = 0.115 g
