Lithium oxide is used aboard the space shuttle to remove...

Lithium oxide is used aboard the space shuttle to remove water from the air supply. If 80.0 $\mathrm{kg}$ of water is to be removed and 65 $\mathrm{kg}$ of $\mathrm{L}_{2} \mathrm{O}$ is available, which reactant is limiting? How many kilograms of the excess reactant remain? $$\mathrm{Li}_{2} \mathrm{O}(s)+\mathrm{H}_{2} \mathrm{O}(g) \longrightarrow 2 \mathrm{LiOH}(s)$$

Lithium oxide is used aboard the space shuttle to remove water from the air supply. If 80.0 $\mathrm{kg}$ of water is to be removed and 65 $\mathrm{kg}$ of $\mathrm{L}_{2} \mathrm{O}$ is available, which reactant is limiting? How many kilograms of the excess reactant remain?
$$\mathrm{Li}_{2} \mathrm{O}(s)+\mathrm{H}_{2} \mathrm{O}(g) \longrightarrow 2 \mathrm{LiOH}(s)$$

Key Concepts

Mole-to-Mass Conversion

Mole-to-mass conversion is a fundamental calculation in chemistry that links the number of moles of a substance to its mass using the substance's molar mass. It enables the practical application of stoichiometric relationships by converting laboratory measurements of mass into the amount of substance in moles for use in chemical equations.

Balanced Chemical Equation

A balanced chemical equation accurately represents the conservation of mass in a chemical reaction by ensuring that the number of each type of atom is the same on both sides of the equation. This is the foundation of stoichiometric calculations and helps in determining the proportions of reactants and products involved.

Stoichiometry

Stoichiometry involves the quantitative relationship between reactants and products in a chemical reaction, based on the balanced chemical equation. It allows chemists to determine how much of each reactant is needed and how much product will result, making it essential for reaction scaling and optimization.

Excess Reactant

The excess reactant is the one that remains even after the reaction has consumed the limiting reactant. Calculating the amount of excess reactant left over is important for understanding resource utilization and for planning any subsequent purification or recycling processes in industrial and laboratory settings.

Limiting Reactant

The limiting reactant is the substance in a chemical reaction that is completely consumed first, determining the maximum amount of product that can be formed. It plays a crucial role in calculating theoretical yields because once the limiting reactant is exhausted, the reaction cannot proceed further, regardless of the quantities of other reactants present.

Transcript

00:02 We are told that we have 65 kilograms of lithium oxide as well as 80 .0 kilograms of water.

00:13 We need to recognize this immediately as a limiting reactant problem when asked for the product because we don't know which of these two reactions is going to run out first.

00:24 So to figure out which reactants is limiting, first we're going to find the number of moles of each reactants.

00:36 For these, we need their molar masses.

00:50 Let's see for lithium oxide and water is 18 .02.

00:59 Now we'll do the math.

01:01 So remember that for mass to mole conversions, we need grams.

01:07 Instead of 65 kilograms, i'm going to start with 65 ,000 grams of l -i -20.

01:16 Divide by its molar mass, 29 .89 grams of l -i -20.

01:22 In every one mole.

01:29 This is equal to 2 ,175 moles.

01:35 Same treatment for water.

01:38 80 ,000 grams of water.

01:46 Change to moles for every one mole of water.