An automobile antifreeze mixture is made by mixing equal...

An automobile antifreeze mixture is made by mixing equal volumes of ethylene glycol $(d=1.114 \mathrm{g} / \mathrm{mL} ; \mathscr{M}=62.07 \mathrm{g} / \mathrm{mol})$ and water $(d=1.00 \mathrm{g} / \mathrm{mL})$ at $20^{\circ} \mathrm{C}$ . The density of the mixture is 1.070 $\mathrm{g} / \mathrm{mL}$ . Express the concentration of ethylene glycol as: (a) Volume percent (b) Mass percent (c) Molarity (d) Molality (e) Mole fraction

An automobile antifreeze mixture is made by mixing equal volumes of ethylene glycol $(d=1.114 \mathrm{g} / \mathrm{mL} ; \mathscr{M}=62.07 \mathrm{g} / \mathrm{mol})$ and water $(d=1.00 \mathrm{g} / \mathrm{mL})$ at $20^{\circ} \mathrm{C}$ . The density of the mixture is 1.070 $\mathrm{g} / \mathrm{mL}$ . Express the concentration of ethylene glycol as:
(a) Volume percent (b) Mass percent (c) Molarity
(d) Molality (e) Mole fraction

Key Concepts

Molarity

Molarity is a concentration measure defined as the number of moles of solute per liter of solution. It is widely used in chemistry for reactions in solution because it directly relates the number of reacting particles to the volume of the overall system.

Volume Percent

Volume percent is a concentration unit defined as the ratio of the volume of a solute to the total volume of the solution, multiplied by 100. It is used when the amounts of substances are measured in volumes and is especially useful when mixing liquids.

Mass Percent

Mass percent, or weight percent, is the ratio of the mass of the solute to the total mass of the solution, expressed as a percentage. It provides a straightforward way to express the concentration of a solution when the masses of both solute and solvent are known.

Molality

Molality is defined as the number of moles of solute per kilogram of solvent. Unlike molarity, molality is independent of temperature and pressure changes since it is based on mass rather than volume, making it useful in situations where temperature variations are significant.

Mole Fraction

Mole fraction is the ratio of the number of moles of a component to the total number of moles present in the mixture. This dimensionless quantity is particularly valuable in thermodynamic calculations and in describing the composition of mixtures, including gaseous systems.

Density

Density, which is the mass per unit volume of a substance, is an essential concept in converting between different concentration units. In solution chemistry, knowing the density allows for the translation of volume measurements into mass, facilitating calculations of mass percent, molarity, and other concentration expressions.

Transcript

00:01 So now we're going to work on problem 77 from chapter 13.

00:06 In this problem, we're told that we have, we're making an anti -freeze mixture by mixing equal volumes of ethylene glycol and water.

00:22 So we're given some information, the density of ethylin glycol and water and the molar mass of ethylin glycol, and we need to calculate volume percent, mass percent, molarity, molality, and mole fraction.

00:35 We're also given the density of the mixture.

00:40 So we're going to need several different parameters to calculate all these concentrations.

00:46 So first we should calculate the mass of ethylene glycol.

00:52 So we're told that they mix equal volumes of this ethlyn glycol and water.

01:00 It does tell us what the volumes are so we can select something that's convenient.

01:05 End.

01:07 So we can choose one liter for each volume.

01:13 So one liter of ethylin glycol.

01:16 And we can convert this to mass first by converting to milliliters, because the density value is given in grams per milliliter, and then multiplying by the density.

01:40 So milliliters and liters cancel, and we get a value of 11, 14 grams.

01:48 Of ethylene glycol.

01:54 So next we can calculate the mass of water.

01:59 The volume that we're given, or the volume that we chose, is one liter.

02:07 We go through exactly the same process.

02:24 The value of density that we're given for water is 1 .00 grams per milliliter.

02:31 So one liter of h2o is a thousand grams of h2o.

02:45 So to calculate all these concentrations, we're going to need moles of each of these solutions, each of these constituents of solutions.

02:55 So moles of ethylin glycol is equal to the mass, which we calculated, times the molar, or divided by the molar mass, which is 68 .02.

03:16 So we have a value of, it's 62 .07.

03:28 Read from the problem incorrectly.

03:31 And so that gives a value of 17 .947 moles.