Answer:
-800 kJ/mol
Explanation:
To solve the problem, we have to express the enthalpy of combustion (ΔHc) in kJ per mole (kJ/mol).
First, we have to calculate the moles of methane (CH₄) there are in 2.50 g of substance. For this, we divide the mass into the molecular weight Mw) of CH₄:
Mw(CH₄) = 12 g/mol C + (1 g/mol H x 4) = 16 g/mol
moles CH₄ = mass CH₄/Mw(CH₄)= 2.50 g/(16 g/mol) = 0.15625 mol CH₄
Now, we divide the heat released into the moles of CH₄ to obtain the enthalpy per mole of CH₄:
ΔHc = heat/mol CH₄ = 125 kJ/(0.15625 mol) = 800 kJ/mol
Therefore, the enthalpy of combustion of methane is -800 kJ/mol (the minus sign indicated that the heat is released).
The Inca “City of the Sun” was the city of Cuzco
Answer:
Mass in kg = 4.7*10^19 kg
Mass in tons = 5.2*10^16 tons
Explanation:
<u>Given:</u>
Total volume of sea water = 1.5*10^21 L
Mass % NaCl in seawater = 3.1%
Density of seawater = 1.03 g/ml
<u>To determine:</u>
Total mass of NaCl in kg and in tons
<u>Calculation:</u>
Unit conversion:
1 L = 1000 ml
The volume of seawater in ml is:
To convert mass from g to Kg:
1000 g = 1 kg
To convert mass from g to tons:
1 ton = 9.072*10^6 g
This means a release of free energy from the system corresponds to a negative change in free energy, but to a positive change for the surroundings.
C is the answer hope the answer is right
