Magnesium metal burns in oxygen to form magnesium oxide,...

Magnesium metal burns in oxygen to form magnesium oxide, MgO. (a) Write a balanced equation for the reaction. (b) How many grams of oxygen are needed to react with 25.0 g of Mg? How many grams of MgO will result? (c) How many grams of Mg are needed to react with 25.0 g of $\mathrm{O}_{2} ?$ How many grams of MgO will result?

Magnesium metal burns in oxygen to form magnesium oxide, MgO.
(a) Write a balanced equation for the reaction.
(b) How many grams of oxygen are needed to react with 25.0 g of Mg? How many grams of MgO will result?
(c) How many grams of Mg are needed to react with 25.0 g of $\mathrm{O}_{2} ?$ How many grams of MgO will result?

Key Concepts

Stoichiometry

Stoichiometry is the quantitative relationship between reactants and products in a chemical reaction. It uses the balanced chemical equation to calculate how much of one substance reacts or forms when a given amount of another substance is involved, typically by converting between grams and moles.

Molar Mass

Molar mass is the mass of one mole of a substance, usually expressed in grams per mole. It serves as a conversion factor to translate between the mass of a substance and the number of moles, which is essential for performing stoichiometric calculations.

Balanced Chemical Equation

This concept involves writing a chemical equation in which the number of atoms for each element is equal on both sides of the reaction. It is based on the law of conservation of mass, ensuring that matter is neither created nor destroyed during the reaction.

Limiting Reactant

The limiting reactant is the substance that is completely consumed first in a chemical reaction, thus limiting the amount of product that can be formed. Identifying the limiting reactant is key to accurately determining the quantities of products that result from the reaction.

Transcript

00:01 Magnesium is a metal, this symbol mg.

00:05 Oxygen is a diatomic molecule when it is found in nature.

00:09 So this is o2.

00:11 When these react, i get an ionic compound form of magnesium 2 plus ions and oxide ions.

00:20 So the formula for magnesium oxide is n -g -o.

00:24 And then after i've written the products, then i can go back and write coefficients.

00:30 Balance the equation.

00:32 If there's one oxygen, one diatomic oxygen, there must be two magnesium oxides.

00:37 And because there are two magnesium atoms on the right, there must be two magnesium atoms on the left.

00:45 In part b, i am starting with 25 grams of magnesium, 25 .0 grams of magnesium.

01:10 And i want to find grams of oxygen to go with that.

01:19 I'm also asked to find grams of magnesium oxide.

01:23 And so when i need to find grams of two different substances in the reaction starting from the same given, it's easiest to just find moles of that given first.

01:34 So according to the molar mass of magnesium, one mole is equivalent to 24 .31 grams, and that's equal to 1 .03 moles of magnesium.

01:48 Why would i want to do that? well, first to find the oxygen, i know that 1 .03 moles of magnesium, we find the equivalent oxygen by using the multiple ratio between magnesium and oxygen.

02:11 So for every one mole of oxygen, there are two moles of magnesium.

02:18 And since i'm ultimately looking for mass, i'm going to multiply by the molar mass of oxygen, which is 32 .00 grams in every one mole.

02:29 Notice that it's 32, not 16.

02:32 That's.

02:32 That's a single oxygen atom.

02:34 And this gives me 16 .5 grams of oxygen.

02:42 I'm also asked for what mass of magnesium oxide is formed.

02:47 And i realize that there's equal molar ratios between magnesium and magnesium oxide...