Assigning oxidation states

What is the oxidation state of chlorine in $\ce{Cl2O7}$? A. $-7$ B. $+3.5$ C. $+7$ D. $+14$

In which species does an atom have the oxidation state +5? I. $\ce{IF5}$ II. $\ce{H3PO4}$ III. $\ce{N2O4}$ A. I and II only B. I and III only C. II and III only D. I, II and III

Sulfur has different oxidation states in hydrogen sulfide, $\ce{H2S}$, and in sulfurous acid, $\ce{H2SO3}$. Which pair of values is correct? A. $\ce{H2S}$: +2; $\ce{H2SO3}$: +4 B. $\ce{H2S}$: −2; $\ce{H2SO3}$: +6 C. $\ce{H2S}$: −2; $\ce{H2SO3}$: +4 D.…

In which compound does nitrogen have an oxidation state of +3? A. $\ce{NH3}$ B. $\ce{HNO2}$ C. $\ce{NO2}$ D. $\ce{HNO3}$

Sulfur dioxide can also be removed from flue gas by reaction with hydrogen peroxide, forming sulfuric acid. $\ce{SO2(g) + H2O2(aq) -> H2SO4(aq)}$ Deduce which element is reduced in this process, indicating the initial and final oxidation states. Element…

Methanoic acid, $\ce{HCOOH(aq)}$, and hydrochloric acid, $\ce{HCl(aq)}$, are both acids. A $0.100\ \mathrm{mol\,dm^{-3}}$ solution of $\ce{HCOOH(aq)}$ has a pH of 2.39 while a solution of $\ce{HCl(aq)}$ of the same concentration has a pH of 1.00. (i) Explain…

What are the oxidation states of the elements in $\ce{K2MnO4}$? A. K: +1, Mn: +6, O: −2 B. K: +1, Mn: +7, O: −2 C. K: +2, Mn: +4, O: −2 D. K: +1, Mn: +6, O: −1

Calcium hydride is used as a portable source of hydrogen for fuel cells. It reacts with water as shown. $\ce{CaH2(s) + 2H2O(l) -> Ca(OH)2(aq) + 2H2(g)}$ Which statement is correct? A. Calcium is reduced from +2 to 0. B. Hydrogen in $\ce{CaH2}$ is oxidized from…