Ethanol in Fuel E-85 is an alternative fuel for automobiles and light trucks that consists of 85

step 1 So we're going to be given some E85 fuel. And E85 is 85 % ethanol by volume. And ethanol is CH3,

Ethanol in Fuel E-85 is an alternative fuel for automobiles...

Key Concepts

Unit Conversion

Unit conversion is the process of converting one unit of measurement to another, such as converting gallons to milliliters or liters. Accurate unit conversions are fundamental in chemistry to ensure that calculations involving volume, mass, and moles are consistent and correctly scaled.

Combustion Reaction

A combustion reaction is a chemical process in which a substance reacts with oxygen to produce combustion products, typically carbon dioxide and water. In the context of ethanol, the balanced combustion reaction shows the precise mole ratio between ethanol and carbon dioxide, which is essential for calculating the amount of carbon dioxide produced.

Stoichiometry

Stoichiometry involves the quantitative relationships between the reactants and products in a chemical reaction. It allows one to use the balanced chemical equation to determine how many moles of products, such as carbon dioxide, are formed from a known amount of reactants, such as ethanol.

Density

Density is the mass per unit volume of a substance. It allows for the conversion between the volume of a material and its mass, which is crucial when you are given a volume (such as a gallon) and need to determine the mass of the ethanol present within it.

Molar Mass

Molar mass is the mass of one mole of a substance and is typically expressed in grams per mole (g/mol). It is used to convert between the mass of a chemical compound and the number of moles, enabling the quantitative analysis of reactions and components.

Moles

The mole is a fundamental unit in chemistry that represents an amount of substance, specifically 6.022×10^23 entities (Avogadro’s number). Knowing the number of moles of a substance is essential for understanding reaction stoichiometry and determining the proportions in which substances react.

Transcript

00:01 So we're going to be given some e85 fuel.

00:05 And e85 is 85 % ethanol by volume.

00:09 And ethanol is ch3, ch2oh.

00:13 And we're told the density of ethanol is 0 .79 grams per millimeter.

00:18 And we want to find out how many moles of ethanol are in one gallon of e85 fuel.

00:27 So first off, we're going to have to find out how many moles of ethanol.

00:31 How many liters since we're given milliliters over here how many liters there are in one gallon so if you look up the conversion factor you'll see that one gallon is equal to 3 .785 liters all right so we're going to put this into mill liters since we're using milliliters up here we just want to get our units right so we'll do 3785 milliliters.

01:06 Alright, so this is 3 ,785 milliliters of e85 fuel, but only 85 % of that is ethanol.

01:15 So we're going to take this 3785 and get 85 % of it, and that'll give us 3217 .6.

01:27 So this is how many milliliters of ethanol are in? e85 fuel.

01:40 The next we're going to have to find out how many grams we have so we can convert our number of ethanol to moles.

01:49 So we'll take our 3217 milliliters, multiply it by 0 .79 grams per milliliter and this will give us the amount of ethanol in grams.

02:03 And this works out to around 25 ,000.

02:08 41.

02:10 We'll go ahead and put a decimal number.

02:14 0 .9 grams.

02:16 All right.

02:18 So now we need to divide this number by the atomic mass of ethanol so we can find out how many moles we have here.

02:26 So we'll take this and divide it by 46 .07, which is the atomic mass of ethanol.

02:36 And you'll see that we get 55 .17.

02:45 So since this density is given to two significant figures, and that's the lowest number of significant figures in this problem, we'll just go ahead and around to two sig figs and say 55 moles.

03:04 So we just found out there are 55 moles of ethanol per gallon, of e85 fuel...

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