Book cover for Living by Chemistry

Living by Chemistry

Angelica M. Stacy

ISBN #9781464142314

2nd Edition

940 Questions

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129,188 Students Helped

Homework Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

Chemical equations serve as essential tools that allow chemists to track changes in matter, both in everyday reactions and in toxicological incidents. By clearly indicating reactants, products, and their physical states, these equations help predict observable changes such as dissolution, gas evolution, and color transformations. Moreover, understanding these equations is critical for managing toxic substances and safeguarding human health.

Learning Objectives

1

Describe the structure of a chemical equation and distinguish between reactants and products.

2

Explain how chemical equations are used to track changes in matter, including both beneficial and toxic reactions.

3

Interpret chemical equations to predict observable evidence such as phase changes, gas evolution, and color changes.

4

Analyze the role of chemical equations in understanding toxic substances and their effects on living organisms.

Key Concepts

CONCEPT

DEFINITION

Chemical Equation

A symbolic representation of a chemical reaction using numbers, chemical formulas, and symbols to show the reactants and products along with their physical states.

Reactants

The starting substances in a chemical reaction that undergo change.

Products

The substances produced as a result of a chemical reaction.

Toxic Reaction

A chemical reaction involving substances that can be hazardous to living organisms, potentially leading to harmful effects or poisoning.

Phase Indicators

Labels (such as (s), (l), (aq), and (g)) in chemical equations that denote the physical state of each reactant and product.

Example Problems

Example 1

What is the difference between a reactant and a product?

Example 2

Are chemicals and chemical reactions important for life? Why or why not?

Example 3

Describe in your own words what a toxic substance is.

Example 4

Both bleach and ammonia are used for cleaning. However, it is very dangerous to mix bleach with ammonia because they react to produce sodium hydroxide and the toxic gas chloramine. $$\mathrm{NaOCl}(a q)+\mathrm{NH}_{3}(a q) \longrightarrow \mathrm{NaOH}(a q)+\mathrm{NH}_{2} \mathrm{Cl}(g)$$ a. Write an interpretation of the chemical equation. b. What do you expect to observe?

Example 5

Poisoning with mercury chloride can be reversed by chelation therapy. The chelating agent called EDTA, $\mathrm{C}_{10} \mathrm{H}_{16} \mathrm{N}_{2} \mathrm{O}_{8},$ is injected into the bloodstream. EDTA forms a water-soluble compound with mercury ions, allowing removal from the body through the kidneys. $$\mathrm{HgCl}_{2}(s)+\mathrm{C}_{10} \mathrm{H}_{16} \mathrm{N}_{2} \mathrm{O}_{8}(a q) \longrightarrow \operatorname{HgC}_{10} \mathrm{H}_{12} \mathrm{N}_{2} \mathrm{O}_{8}(a q)+4 \mathrm{HCl}(a q)$$ a. Write an interpretation of the chemical equation. b. What do you expect to observe?
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Step-by-Step Explanations

QUESTION

How does the chemical equation 2HCl(aq) + Cr(s) → CrCl2(aq) + H2(g) indicate what you would observe in the experiment?

STEP-BY-STEP ANSWER:

Step 1: Identify the reactants and products. Reactants are hydrochloric acid (HCl) in aqueous form and solid chromium (Cr), while the products are aqueous chromium (II) chloride (CrCl2) and hydrogen gas (H2).
Step 2: Note the phase indicators to understand the state of each substance. HCl(aq) is in solution, Cr(s) is a solid, CrCl2(aq) is in solution, and H2(g) is a gas.
Step 3: Analyze the changes. The disappearance of the solid chromium and the formation of hydrogen gas bubbles indicate the progression of the reaction.
Step 4: Make observational predictions. You would expect to see the solid chromium dissolving, the formation of a new aqueous solution, and gas bubbles forming as hydrogen is released.
Final Answer: The equation indicates that when solid chromium reacts with hydrochloric acid, it dissolves to form an aqueous chromium (II) chloride solution, and hydrogen gas is released as bubbles.

Interpreting the Chromium Reaction

QUESTION

Given the chemical equation NaOCl(aq) + NH3(aq) → NaOH(aq) + NH2Cl(g), how would you describe the reaction and its observable outcomes?

STEP-BY-STEP ANSWER:

Step 1: Identify the reactants and products. Reactants are sodium hypochlorite (NaOCl) and ammonia (NH3), both in aqueous solutions. The products are sodium hydroxide (NaOH) in aqueous form and chloramine (NH2Cl) as a gas.
Step 2: Recognize the implications of each substance. The formation of NaOH indicates a shift in pH, and the production of a gas (chloramine) can make the reaction hazardous.
Step 3: Predict observable changes. In a laboratory setting, you might not see dramatic color changes, but you would observe the evolution of gas bubbles indicative of chloramine formation.
Step 4: Connect it to safety. The reaction produces toxic gas, so proper safety measures must be in place when mixing these chemicals.
Final Answer: The reaction between sodium hypochlorite and ammonia results in the formation of aqueous sodium hydroxide and toxic chloramine gas, with observable gas bubbles indicating the reaction.

Interpreting a Toxic Reaction

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Common Mistakes

  • Confusing reactants with products in a chemical equation.
  • Ignoring phase indicators, which provide crucial information about the states of substances.
  • Overlooking that some chemical changes, although not immediately visible, are still significant (e.g., colorless reactions).
  • Assuming that all reactions produce dramatic observable changes, when some may occur without noticeable effects.