Methanol, CH3 OH, is a clean-burning, easily handled fuel....

Methanol, $\mathrm{CH}_{3} \mathrm{OH},$ is a clean-burning, easily handled fuel. It can be made by the direct reaction of $\mathrm{CO}$ and $\mathrm{H}_{2}$. $$\mathrm{CO}(\mathrm{g})+2 \mathrm{H}_{2}(\mathrm{~g}) \longrightarrow \mathrm{CH}_{3} \mathrm{OH}(\ell)$$ (a) For a mixture of $12.0 \mathrm{~g} \mathrm{H}_{2}$ and $74.5 \mathrm{~g} \mathrm{CO},$ determine the limiting reactant. (b) Calculate the mass (g) of the excess reactant left after reaction is complete. (c) Calculate the theoretical mass of methanol that can be obtained.

Methanol, $\mathrm{CH}_{3} \mathrm{OH},$ is a clean-burning, easily handled fuel. It can be made by the direct reaction of $\mathrm{CO}$ and $\mathrm{H}_{2}$.
$$\mathrm{CO}(\mathrm{g})+2 \mathrm{H}_{2}(\mathrm{~g}) \longrightarrow \mathrm{CH}_{3} \mathrm{OH}(\ell)$$
(a) For a mixture of $12.0 \mathrm{~g} \mathrm{H}_{2}$ and $74.5 \mathrm{~g} \mathrm{CO},$ determine the limiting reactant.
(b) Calculate the mass (g) of the excess reactant left after reaction is complete.
(c) Calculate the theoretical mass of methanol that can be obtained.

Key Concepts

Theoretical Yield

The theoretical yield is the calculated maximum amount of product that can be generated from a given amount of limiting reactant, based on the stoichiometry of the reaction. This concept is pivotal in predicting the efficiency of a reaction and in planning industrial-scale chemical processes.

Excess Reactant

The excess reactant is the substance that remains after the reaction has gone to completion, once the limiting reactant has been completely consumed. It is important to calculate the leftover amount of an excess reactant to account for resource efficiency and potential further processing.

Stoichiometry

Stoichiometry involves the quantitative relationships between the amounts of reactants and products in a chemical reaction. It uses the balanced chemical equation to determine the proportions and the conversion factors needed to relate moles of different substances, underpinning most calculations in chemical synthesis and reaction yield.

Limiting Reactant

The limiting reactant is the substance that is completely consumed first in a chemical reaction, dictating the maximum amount of products that can be formed. Understanding and identifying the limiting reactant is essential for predicting yields and optimizing the use of materials in a reaction.

Molar Mass and Conversion

Molar mass is the mass of one mole of a substance and serves as a bridge between the mass of a substance and the number of moles. Converting between grams and moles using the molar mass is crucial in stoichiometric calculations, enabling accurate determination of reactant amounts and product yields.

Transcript

00:01 Let's take a look at the synthesis of methanol from carbon monoxide and hydrogen.

00:06 And let's say we start with 74 and a half grams of carbon monoxide and 12 grams of hydrogen.

00:19 Let's figure out what the limiting reactant is.

00:22 So to figure out limiting reactant, we should go to our product and we should choose the one that gives us fewer moles.

00:29 And so let's go ahead and start with our carbon monoxide.

00:38 We have to convert to grams using molar mass, and the molar mass of carbon monoxide is 28 .01 grams.

00:52 Then we want to go to methanol, and we create one mole of methanol for every one mole of carbon monoxide we use, getting them from the coefficients of our balanced equation.

01:08 And we multiply, i'm sorry, we'll stop right here.

01:13 And when we stop right here, we're going to find out how many moles we would make of methanol.

01:21 And it turns out that we would make 2 .66 moles.

01:29 We're going to do the same thing with our hydrogen.

01:32 We have 12 grams.

01:41 And the molar mass of h2 is 2 .016 grams.

01:46 Mole ratio here for every one mole with methanol we make, we have to use, look at the coefficient, two moles of hydrogen, and when you do the math on that, you find you get 2 .98 moles of methanol.

02:07 So the lower value is 2 .66.

02:10 That implies that co is the limiting reactant.

02:16 So carbon monoxide is our limiting reactant.

02:21 And let's say we wanted to figure out how much or how many grams of the excess reactant was left over...

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