Chapter 13

Name the reactants, products, and catalyst for photosynthesis. What is the source of the necessary energy?

Iodine is a (a) blue-black, (b) crystalline, and (c) solid. It (d) sublimes to a violet-colored gas and (e) reacts with aluminum and many other metals. Which of these five properties are physical, and which are chemical?

Classify each of the following as either a physical change or a chemical change. (a) dissolving sugar in water (b) crushing rock salt (c) burning sulfur (d) digesting a chili dog

What are some clues that a chemical reaction has occurred?

In a chemical reaction, explain what happens to the reactants, products, and energy.

What is the difference between coefficients and subscripts in a balanced chemical equation?

The following reaction occurs when a butane cigarette lighter is operated: $C_4{\mathrm{H}}_{10}+{\mathrm{O}}_2⟶{\mathrm{CO}}_2+{\mathrm{H}}_2\mathrm{O}.$ When balancing the equation, you should not start with which element?

What is inappropriate about each of the "balanced" equations shown? (a) ${\mathrm{C}}_4{\mathrm{H}}_{10}+\frac{13}{2}{\mathrm{O}}_2⟶4{\mathrm{CO}}_2+5{\mathrm{H}}_2\mathrm{O}$ (b) $4{\mathrm{H}}_2\mathrm{O}⟶2{\mathrm{O}}_2+4{\mathrm{H}}_2$ (c) $\mathrm{Na}+{\mathrm{H}}_2\mathrm{O}⟶\mathrm{NaOH}+\mathrm{H}$ (d) $\mathrm{He}+{\mathrm{Br}}_2⟶{\mathrm{HeBr}}_2$

Tell what is indicated by each of these six symbols sometimes seen in chemical reactions: $(aq),(s),(l),(g),⟶,$ and $\rightleftharpoons ,$ and by a chemical formula written above a reaction arrow.

Describe the type of reaction for each reaction shown. (a) $2{\mathrm{H}}_2\mathrm{O}⟶2{\mathrm{H}}_2+{\mathrm{O}}_2$ (b) $2\mathrm{Ca}+{\mathrm{O}}_2⟶2\mathrm{CaO}$ (c) $2{\mathrm{NaN}}_3(\mathrm{s})⟶2\mathrm{Na}(\mathrm{s})+3{\mathrm{N}}_2(g)$