Molar mass can be determined by adding the atomic masses of each individual element, depending on how many times they appear. You can find how many times they appear by looking at their respective subscripts. Atomic masses of each element can be found on the periodic table.
For example, in #1
Multiply the mass of Lithium (6.941) by 4, because there are 4 lithium molecules.
Multiple the mass of Phosphorus (30.974) by 2 because there are 2 Phosphorus molecules.
And multiply the mass of oxygen (15.999) by 7 because there are 7 oxygen molecules.
After you have those values, add them together to find the total molar mass of the compound.
Answer:
1.356x10⁻²¹ grams.
Explanation:
mass of carbon containing 68 atoms = 12g Carbon/6.02x10²³atoms = 1.993x10⁻²³ g/atom x 68 atoms = 1.356x10⁻²¹ grams.
Gasoline contains C and H atoms. During combustion, the carbon (C) from the fuel combines with oxygen (O2) from the air to produce carbon dioxide (CO2).
2 C8H18 + 25 O2 → 16 CO2 + 18 H2O.
Combustion reactions release large amounts of heat. They have negative enthalpy. A negative enthalpy represents an exothermic reaction, releasing heat. This reaction is spontaneous and exothermic, since we can obtain energy from the reaction; the ΔG (free energy) is negative (So 1 is true).
ΔG < 0, so the free energy of the system decreases with the reaction. Remember that when there is a negative ΔG the reaction goes from higher free energy to lower free energy, like in this case.