A compound of carbon and hydrogen consists of $94.34 \% \mathrm{C}$ and $5.66 \% \mathrm{H}$, by mass. The molecular mass of the compound is found to be $178 \mathrm{u}$. What is its molecular formula?

Diethylene glycol, used to de-ice aircraft, is a carbonhydrogen-oxygen compound with $45.27 \% \mathrm{C}$ and $9.50 \% \mathrm{H}$ by mass. What is its empirical formula?

How does a scientific theory compare with a scientific hypothesis?

Determine the percent, by mass, of the indicated element: $\mathrm{Mg}$ in chlorophyll, $\mathrm{C}_{55} \mathrm{H}_{72} \mathrm{MgN}_4 \mathrm{O}_5$, the green pigment in plant cells

Determine the percent, by mass, of the indicated element: $\mathrm{Fe}$ in Prussian blue, $\mathrm{Fe}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right]_3$, a pigment used in paints and printing inks

Determine the percent, by mass, of the indicated element: Pb in tetraethyl lead, $\mathrm{Pb}\left(\mathrm{C}_2 \mathrm{H}_5\right)_4$, once extensively used as an additive to gasoline to prevent engine knocking

Determine the mass percent $\mathrm{H}$ in the hydrocarbon isooctane, $\mathrm{C}\left(\mathrm{CH}_3\right)_3 \mathrm{CH}_2 \mathrm{CH}\left(\mathrm{CH}_3\right)_2$.

The hemoglobin content of blood is about $15.5 \mathrm{~g} / 100 \mathrm{~mL}$ blood. The molar mass of hemoglobin is about $64,500 \mathrm{~g} / \mathrm{mol}$, and there are four iron (Fe) atoms in a hemoglobin molecule. Approximately how many Fe atoms are present in the $6 \mathrm{~L}$ of blood in a typical adult?

Acetaminophen, an analgesic and antipyretic drug, has a molecular mass of $151.2 \mathrm{u}$ and a mass percent composition of $63.56 \% \mathrm{C}, 6.00 \% \mathrm{H}, 9.27 \%$ $\mathrm{N}$, and $21.17 \% \mathrm{O}$. What is the molecular formula of acetaminophen?

Appendix E describes a useful study aid known as concept mapping. Using the method presented in Appendix E, construct a concept map illustrating the different concepts in Sections 3-2 and 3-3.

The greatest number of $\mathrm{N}$ atoms is found in (a) $50.0 \mathrm{~g}$ $\mathrm{N}_2 \mathrm{O}$; (b) $17.0 \mathrm{~g} \mathrm{NH}_3$; (c) $150 \mathrm{~mL}$ of liquid pyridine, $\mathrm{C}_5 \mathrm{H}_5 \mathrm{~N}(d=0.983 \mathrm{~g} / \mathrm{mL})$; (d) $1.0 \mathrm{~mol} \mathrm{~N}_2$.

For the mineral torbernite, $\mathrm{Cu}\left(\mathrm{UO}_2\right)_2\left(\mathrm{PO}_4\right)_2 \cdot 8 \mathrm{H}_2 \mathrm{O}$, determine the mass required to contain $1.00 \mathrm{~g} \mathrm{P}$

For the mineral torbernite, $\mathrm{Cu}\left(\mathrm{UO}_2\right)_2\left(\mathrm{PO}_4\right)_2 \cdot 8 \mathrm{H}_2 \mathrm{O}$, determine the element present in the greatest mass percent

For the mineral torbernite, $\mathrm{Cu}\left(\mathrm{UO}_2\right)_2\left(\mathrm{PO}_4\right)_2 \cdot 8 \mathrm{H}_2 \mathrm{O}$, determine the ratio, by mass, of $\mathrm{Cu}$ to $\mathrm{P}$