Ethanol, c2h6o, is most often blended with gasoline - usually as a 10 percent mix - to create a fuel called gasohol. ethanol is a renewable resource and ethanol-blended fuels, like gasohol, appear to burn more efficiently in combustion engines. the heat of combustion of ethanol is 326.7 kcal/mol. the heat of combustion of octane, c8h18, is 1.308×103 kcal/mol. how much energy is released during the complete combustion of 406 grams of octane ? kcal assuming the same efficiency, would 406 grams of ethanol provide more, less, or the same amount of energy as 406 grams of octane?

Explanation:

Given,

The heat of combustion of octane = 1.308×10³ kcal/mol

It means that combustion of 1 mole of octane produces 1.308×10³ kcal of energy

Given mass = 406 g

Molar mass of octane = 114.23 g/mol

The formula for the calculation of moles is shown below:

Thus,

Moles of octane = 3.5542 moles

Combustion of 3.5542 moles produces 3.5542×1.308×10³ kcal of energy

Energy released from 406 grams of octane = 4.649×10³ kcal

Also given,

The heat of combustion of ethanol = 326.7 kcal/mol

It means that combustion of 1 mole of octane produces 326.7 kcal of energy

Given mass = 406 g

Molar mass of octane = 46.07 g/mol

The formula for the calculation of moles is shown below:

Thus,

Moles of octane = 8.8127 moles

Combustion of 8.8127 moles produces 8.8127×326.7 kcal of energy

Energy released from 406 grams of ethanol= 2879.11 kcal = 2.879×10³ kcal

It is less.

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g