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. $\ce{HNO3}$

In the Claus process, used to recover sulfur from refinery gases, sulfur dioxide reacts with hydrogen sulfide, $\ce{H2S}$, to form sulfur. (i) State the oxidation state of sulfur in $\ce{SO2}$ and in the sulfur produced. (ii) Deduce the balanced equation for…

Methanoic acid, $\ce{HCOOH}$, is a weak acid, and solutions of it are often used as acidic buffers. A chemist prepared a $0.500\ \mathrm{mol\,dm^{-3}}$ solution of methanoic acid, in which two conjugate acid–base pairs are present. (i) For each pair, state the…

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

Which row identifies the oxidizing agent and the reducing agent in the reaction below? $\ce{3Cu(s) + 2NO3^-(aq) + 8H+(aq) -> 3Cu^2+(aq) + 2NO(g) + 4H2O(l)}$ A. Oxidizing agent: $\ce{Cu}$, reducing agent: $\ce{NO3^-}$ B. Oxidizing agent: $\ce{NO3^-}$, reducing…

Which statements are correct for the complex ion $\ce{[CoCl4]^2-}$? I. The oxidation state of cobalt is +4. II. The chloride ions act as Lewis bases. III. The coordination number of cobalt is 4. A. I and II only B. I and III only C. II and III only D. I, II…

What is the oxidation state of chromium in the complex $\ce{[Cr(NH3)4Cl2]Cl}$? A. +1 B. +2 C. +3 D. +7

Deduce the oxidation state of chlorine in each of the three chlorine-containing species in the equation. $\ce{Cl2}$: $\ce{HOCl}$: $\ce{Cl-}$:

Chloride ions can act as ligands towards transition metal ions. Three compounds of chromium that differ in the number of chloride ions bonded directly to the chromium ion have the formulas and colours shown. Compound Colour $\ce{[Cr(H2O)6]Cl3}$ violet…

Which element forms a stable compound in which its oxidation state is +6? A. Ti B. V C. Cr D. Zn

The overall reaction during the discharge of a lead–acid battery is: $\ce{Pb(s) + PbO2(s) + 2H2SO4(aq) -> 2PbSO4(s) + 2H2O(l)}$ Which statement is correct? A. The oxidation state of lead in $\ce{Pb(s)}$ changes from +2 to 0. B. The oxidation state of sulfur…