Chapter 3: Stoichiometry

You may have noticed that water sometimes drips from an exhaust pipe of a car as it is running.Is this evidence that there is at least a small amount of water originally present in the gasoline?Explain.

Consider the equation $\mathit{A}\mathbf{+}\mathbf{2}\mathit{B}\mathbf{\to }\mathit{A}{\mathit{B}}_{\mathbf{2}}$ Imagine that 10 moles of A is reacted with 26 moles of B.Use a scale from 0 to 10 to express your level of agreement with each of the following statements. Justify and discuss your responses.
a. There will be some As left over.
b. There will be some Bs left over.
c. Because of leftover As, some ${\mathit{A}}_{\mathbf{2}}$molecules will be formed.
d. Because of leftover Bs, some ${\mathit{B}}_{\mathbf{2}}$molecules will be formed.
e. Even if A is not limiting, ${\mathit{A}}_{\mathbf{2}}$ molecules will be formed.
f. Even if B is not limiting, role="math" localid="1662120548192" ${\mathit{B}}_{\mathbf{2}}$ molecules will be formed.
g. Along with the molecule AB₂, molecules with the formula ${\mathit{A}}_{\mathbf{x}}\mathbf{}{\mathit{B}}_{\mathbf{Y}}$(other than$\mathit{A}{\mathit{B}}_{\mathbf{2}}$ ) will be formed.

What information do we get from a formula? From an equation?

One part of the problem -solving strategy for empirical formula determination is to base the calculation on 100g of compound. What if you chose a mass other than 100g? Would this work? What if you chose to base the calculation on 100 moles of compound? Would this work?

What if a friend was balancing chemical equations by changing the values of the subscripts instead of using the coefficients? How would you explain to your friend that this was the wrong thing to do?

Nitrogen (${\mathbf{N}}_{\mathbf{2}}$) and hydrogen (${\mathbf{H}}_{\mathbf{2}}$) react to form ammonia (${\mathbf{NH}}_{\mathbf{3}}$). Consider the mixture of ${\mathbf{N}}_{\mathbf{2}}$() and ${\mathbf{H}}_{\mathbf{2}}$() in a closed container as illustrated:

Assuming that the reaction goes to completion, draw a representation of the product mixture.Explain how you arrived at this representation.

Your lab partner has made the observation that you always take the mass of chemicals in lab, but then use mole ratios to balance the equation. “Why not use the masses in the equation?”, your partner asks. What if your lab partner decided to balance equations by using masses as coefficients? Is this even possible? Why or why not?

For the preceding question, which of the following equations best

represents the reaction?

${\mathbf{\text{a.6N}}}_{\mathbf{2}}\mathbf{+}\mathbf{6}{\mathbf{H}}_{\mathbf{2}}\to \mathbf{4}{\mathbf{NH}}_{\mathbf{3}}\mathbf{+}\mathbf{4}{\mathbf{N}}_{\mathbf{2}}$

${\mathbf{\text{b.N}}}_{\mathbf{2}}\mathbf{+}{\mathbf{H}}_{\mathbf{2}}\to {\mathbf{NH}}_{\mathbf{3}}$

$\mathbf{\text{c.N+3H}}\text{→}{\mathbf{\text{NH}}}_{\mathbf{3}}$

${\mathbf{\text{d.N}}}_{\mathbf{2}}\mathbf{+}\mathbf{3}{\mathbf{H}}_{\mathbf{2}}\to \mathbf{2}{\mathbf{NH}}_{\mathbf{3}}$

${\mathbf{\text{e.2N}}}_{\mathbf{2}}\mathbf{+}\mathbf{6}{\mathbf{H}}_{\mathbf{2}}\to \mathbf{4}{\mathbf{NH}}_{\mathbf{3}}$

You know that chemical A reacts with chemical B. You react 10.0 g A with 10.0 g B. Whatinformation do you need to have to determine the amount of product that will be produced?Explain.

A kerosene lamp has a mass of 1.5 kg. You put 0.5 kg of kerosene in the lamp. You burn all thekerosene until the lamp has a mass of 1.5 kg. What is the mass of the gases that are given off?Explain.