An unknown metal reacts with oxygen to give the metal oxide,...

Key Concepts

Mass Conservation

The principle of mass conservation states that in a chemical reaction, the total mass of reactants is equal to the total mass of products. This fundamental concept is essential when determining the contributions of each element in a reaction, such as calculating how much oxygen has combined with a metal by comparing the mass of the original metal sample to that of the resulting oxide.

Mole Concept

The mole concept is the quantitative relationship between the mass of a substance and the number of atoms or molecules it contains, using Avogadro's number. It serves as a bridge between the atomic scale and the mass scale, enabling the calculation of moles from a given mass and the subsequent determination of the number of particles involved in chemical reactions.

Stoichiometry

Stoichiometry involves the use of balanced chemical equations to calculate the relative quantities of reactants and products in a chemical reaction. This concept allows one to convert measured masses into moles, apply the molar ratios from the reaction equation, and thereby determine unknown quantities such as the identity or molar mass of a reactant or product.

Percent Composition

Percent composition is the method of determining the percentage by mass of each element within a compound. By analyzing the mass contributions of different elements, one can deduce information about the compound's formula and thereby infer characteristics such as the atomic weight of elements when combined with stoichiometric calculations.

Transcript

00:03 Hello, in this problem, we have an unknown metal that we are just going to call m, and it is reacting with oxygen to produce an oxide of the metal.

00:23 And our task is to identify this metal.

00:27 What metal is it? we are given some information.

00:32 We have 0 .356 grams of the metal.

00:38 And we produce 0 .452 grams of the metal oxide.

00:48 All right.

00:50 I propose that to determine the identity of this metal that we determine its molar mass.

00:57 Because if we find its molar mass, we can look for that molar mass on the periodic table and identify this unknown metal in that manner.

01:05 We know that molar mass is defined as grams per mole.

01:16 So on the reactant side, i'd already have grams of the metal.

01:20 If i could figure out how many moles i have, i could then calculate the molar mass.

01:26 So let's go about seeing if there is a way that we can figure that out.

01:30 The product is not going to help us too much because, again, we don't know what the metal is.

01:36 And at first glance, we don't know anything about the oxygen.

01:40 But if we look at this more closely and we think about the law of conservation of mass, we can figure out how many grams of oxygen are reacting.

01:49 The law of conservation of mass says you cannot create or lose mass in a chemical reaction.

01:55 So the mass of the reactants added together has to equal the mass of the product.

02:01 Ah, now we have a plan.

02:03 If i take the mass of the product, 0 .452 grams, and i subtract the mass of the reactant, the difference has to be the mass of the oxygen.

02:24 And that difference is 0 .096.

02:33 Ah, now we have a plan...

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