Calculate the number of atoms, molecules, or formula units...

Calculate the number of atoms, molecules, or formula units that are in each given mass.
a) 85.5 g beryllium nitrate
b) 9.42 g manganese
c) $0.0948 \mathrm{g} \mathrm{C}_{3} \mathrm{H}_{7} \mathrm{OH}$

Key Concepts

Molar Mass

Molar mass is the mass of one mole of a substance, expressed in grams per mole. It is calculated by summing the atomic masses of all atoms in a molecule or formula unit and is used to convert between the mass of a substance and the number of moles present.

Avogadro's Number

Avogadro's number, approximately 6.022 x 10^23, is the number of atoms, molecules, or formula units in one mole of a substance. It provides the bridge between the microscopic scale of individual particles and the macroscopic measure of a substance’s amount.

Mole Concept

The mole concept is a fundamental chemical principle that defines the amount of substance in terms of the number of particles. It allows chemists to count atoms, molecules, or formula units by relating mass measurements to the number of entities using molar mass and Avogadro's number.

Transcript

00:02 Hello, in this problem, we actually have three separate problems that are all extremely similar.

00:09 We are given grams, and we are asked to calculate the number of particles of each substance we have.

00:15 So that could either be atoms, it could be molecules, or it could be formula units depending upon the compound.

00:23 So getting started, in letter a, we are given 85 .5 grams of beryllium nitrate, since beryllium.

00:40 Has a 2 plus charge, i'm going to need two nitrates.

00:46 So we have grams and we're trying to get to number of formula units.

00:52 I am going to have to first divide by the molar mass of this to get to moles, and then i can use avogadro's number to determine the total number of formula units.

01:04 So two steps.

01:05 Let's go ahead and get started.

01:06 The first step is going to be dividing by the molar mass.

01:10 The molar mass is 133 .033 grams.

01:20 And this is, of course, of the beryllium nitrate.

01:24 And that's how many grams there are in every mole.

01:29 This is molar mass.

01:30 So that tells us the number of grams in every mole of beryllium nitrate.

01:43 If we were to solve this problem right now, we would have an answer in moles of berylium nitrate.

01:49 But we are trying to determine the number of formula units.

01:52 So i'm going to have to take it one more step where i multiply by avogadro's number.

01:58 Avogadro's number is 6 .02 times 10 to the 23rd.

02:04 In this case, it's formula units of the berylium nitrate in every mole of berylium nitrate.

02:36 By canceling mole from our numerator with mole from our denominator, we see that our answer is going to be in formula units, which is what we were looking for in this problem.

02:48 So let's go ahead and do the math, and we get 3 .87 times 10 to the 23rd formula units of the berylium nitrate.

03:12 There's our answer for part a.

03:15 So we're a third of the way there.

03:17 Moving on to part b.

03:22 In part b, we are given 9 .42 grams of mn.

03:33 Mn is an element, so we are trying to determine the number of atoms we have...

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