How many moles and how many ions of each type are present in each of the following? (a) 130. mL

How many moles and how many ions of each type are present in...

Key Concepts

Stoichiometry of Ionic Compounds

Stoichiometry in the context of ionic compounds involves using the chemical formula to determine the relative number of moles of each ion produced upon dissolution. It is essential for calculating the total number of ions present based on the moles of the compound.

Ion Dissociation

Ion dissociation refers to the separation of an ionic compound into its constituent ions when it dissolves in a solvent. Understanding the dissociation process allows one to determine the ratio in which different ions are produced from a given formula unit.

Avogadro's Number

Avogadro's number, approximately 6.022 x 10^23, is the number of particles contained in one mole of any substance. This constant is used to convert between the number of moles and the actual number of individual ions, molecules, or atoms.

Molarity

Molarity is a measure of concentration expressed as the number of moles of solute per liter of solution. It is fundamental for converting volumes of a solution into moles of dissolved substances.

Dimensional Analysis

Dimensional analysis involves the use of conversion factors to change units from one form to another, such as converting milliliters to liters. This process is crucial when calculating quantities like moles or ions from given volumes and concentrations.

Solution Concentration Conversion

Solution concentration conversion encompasses the process of translating concentration units, such as from grams per liter to moles per liter, through the use of a substance’s molar mass. This conversion is vital for bridging mass-based measurements with mole-based calculations in solution chemistry.

Transcript

00:02 Okay, we are asked to write how many moles and how many ions of each type of particle.

00:29 And we are given for a, 130 milliliters of 0 .45 molar aluminum chloride.

00:44 And i'm going to make a note here, one mole of aluminum chloride contains one mole of aluminum ions and three moles of chloride ions, as you should be able to see.

01:06 Okay, so if i've got 130 milliliters and there's 1000 milliliters per liter and 0 .45 moles of aluminum chloride per liter, i will get, this can be reported to two significant figures, so i'll take 130 divided by 1000 times 0 .45.

01:41 And i get 0 .0585 equals 0 .059 moles of aluminum chloride.

01:57 That will give me 0 .059 moles of aluminum ion and 0 .059 times three equals, move this over a little bit, equals 0 .176 0 .18 moles of chloride ion.

02:25 There's my first two answers.

02:34 Now i'm going to get number of atoms or number of ions by multiplying by avogadro's number.

03:11 Okay, let me grab my calculator, 0 .05 times 6 .022 times 10 to the 23rd, oopsie, 0 .059.

03:37 Okay, so now i'm going to go ahead, i'm going to not report this, i'm going to go 0 .0585 times avogadro's will be 3 .5 times 10 to the 22nd al3 plus ions.

04:04 Then if i just take that times three again, of 1 .06 or 1 .1 times 10 to the 23rd cl minus ions.

04:20 So here's my answers for part a.

04:32 Now we're going to go do the same thing for part b, and in b we're given 9 .8 milliliters, which is 0 .00980 liters of 9 .59 grams of lithium sulfate, 9 .59 grams per liter.

05:15 Lithium sulfate, oh i don't, i just restarted my computer so i don't have all my tabs open.

05:21 Let me go to a molar mass calculator.

05:27 I've been using the one that starts with an n, not my favorite.

05:32 I wonder if omni is any good.

05:34 No, i guess i'll use my lentec.

05:50 So this will be li2so4, li2so4.

05:56 That is a molar mass of 109 .94 grams per mole will equal 9 .59 divided by 109 .94 0 .08723 moles per liter.

06:19 Then i'm going to take 0 .00980 liters times 0 .08723 moles per liter, and this will equal, i wrote the wrong number here.

07:03 No i didn't.

07:04 Let's see, 0 .0098 times 0 .08723.

07:26 This will be 8 .548 times 10 to the minus fourth, and then i have 8 .54854 times 10 to the minus fourth moles of lithium sulfate, and i'll multiply this by two moles of lithium ion per one mole of lithium 2 sulfate...

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