13. What is an oxidation-reduction reaction? 14. Calcium reacts with oxygen to form calcium oxide. Which reactant is oxidized in this reaction? 15. Is the following sentence true or false? When calcium reacts with oxygen, each calcium atom gains two electrons and becomes a calcium ion with a charge of \( 2- \). 16. Is the following sentence true or false? Oxygen must be present in order for an oxidation-reduction reaction to take place. 17. The process in which an element gains electrons during a chemical reaction is called

possible Find the hydrogen ion concentration of a solution whose pH is 7.1 . Use the formula \( \mathrm{pH}=-\log \left[\mathrm{H}^{+}\right] \)

10 Essay 5 points Please identify the following components for the element Selenium: 1 Chemical Symbol 2. Atomic Number 3. Family \# 4. Valence Electrons 5. Category Edit View Insert Format Tools Table

Which fermula represents an ionic compound? 1. \( \mathrm{H}_{2} \) 2. \( \mathrm{CH}_{4} \) 3. \( \mathrm{CH}_{3} \mathrm{OH} \) 4. \( \mathrm{NH}_{4} \mathrm{Cl} \)

14 Nitrogen has atomic number 7 and oxygen has atomic number 8 What is total number of electrons in \( \left(\mathrm{NO}_{3}\right)^{-} \)ion ? \( \begin{array}{ll}\text { (a) } 15 \mathrm{e}^{-} & \text {(b) } 31 \mathrm{e}^{-} \\ \text {(c) } 32 \mathrm{e}^{-} & \text {(d) } 46 \mathrm{e}^{-}\end{array} \)

Based on bond type, which compound has the highest melting point? 1. \( \mathrm{CH}_{3} \mathrm{OH} \) 2. \( \mathrm{C}_{6} \mathrm{H}_{14} \) 3. \( \mathrm{CaCl}_{2} \) 4. \( \mathrm{CCl}_{4} \)