91Ó°ÊÓ

Which of these terms, (i) mixture, (ii) solid, (iii) liquid, (iv) gas, (v) chemical element, (vi) chemical compound, applies to the following substances at room temperature? (a) Gasoline (b) Iodine (c) Water (d) Air (e) Blood (f) Sodium hydrogen carbonate (g) Gaseous ammonia (h) Silicon

Hydrogen peroxide, often used in solutions to cleanse cuts and scrapes, breaks down to yield water and oxygen: Hydrogen peroxide, \(\mathrm{H}_{2} \mathrm{O}_{2}(a q) \rightarrow\) $$ \text { Hydrogen, } \mathrm{H}_{2}(g)+\text { Oxygen }, \mathrm{O}_{2}(g) $$ (a) Identify the reactants and products. (b) Which of the substances are chemical compounds, and which are elements?

When sodium metal is placed in water, the following change occurs: Sodium, \(\mathrm{Na}(s)+\) Water, \(\mathrm{H}_{2} \mathrm{O}(l) \rightarrow\) Hydrogen, \(\mathrm{H}_{2}(g)+\) Sodium hydroxide, \(\mathrm{NaOH}(a q)\) (a) Identify the reactants and products and their physical states (b) Which of the substances are elements, and which are chemical compounds?

What is the most abundant element in the earth's crust? In the human body? List the name and symbol for each.

Correct the following statements. (a) Carbon dioxide has the formula CO2. (b) Carbon dioxide has the formula \(\mathrm{Co}_{2}\). (c) Table salt, \(\mathrm{NaCl}\), is composed of nitrogen and chlorine.

How many picograms are in \(1 \mathrm{mg}\) ? In \(35 \mathrm{ng}\) ?

How many microliters are in \(1 \mathrm{~L} ?\) In \(20 \mathrm{~mL}\) ?

How many significant figures does each of the following numbers have? (a) 237,401 (b) 0.300 (c) 3.01 (d) 244.4 (e) 50,000 (f) 660

How many significant figures are there in each of the following quantities? (a) Distance from New York City to Wellington, New Zealand, \(14,397 \mathrm{~km}\) (b) Average body temperature of a crocodile, \(299 \mathrm{~K}\) (c) Melting point of gold, \(1337 \mathrm{~K}\) (d) Diameter of an influenza virus, \(0.00001 \mathrm{~mm}\) (e) Radius of a phosphorus atom, \(0.110 \mathrm{nm}\)

Carry out the following conversions: (a) \(3.614 \mathrm{mg}\) to centigrams (b) \(12.0 \mathrm{~kL}\) to megaliters (c) \(14.4 \mu \mathrm{m}\) to millimeters (d) \(6.03 \times 10^{-6} \mathrm{cg}\) to nanograms (e) \(174.5 \mathrm{~mL}\) to deciliters (f) \(1.5 \times 10^{-2} \mathrm{~km}\) to centimeters