Are you ready to master oxidation state practice and sharpen your chemistry prowess? Whether you're a high school student tackling redox reactions or a budding scientist aiming for precision, our free quiz offers the ultimate oxidation numbers practice to test and practice oxidation numbers under realistic conditions. You'll develop skills in assigning oxidation numbers practice while working through challenging oxidation number practice problems that reinforce every rule. This interactive oxidation numbers quiz guides you through fundamental rules - like oxygen's typical state or variable metal valencies - with instant feedback. Then broaden your expertise in our chemistry practice quiz and elevate your confidence. Dive in now, challenge your knowledge, and conquer oxidation states today!
What is the oxidation state of oxygen in H2O?
-2
+2
-1
0
In water, each hydrogen has an oxidation state of +1, giving a total of +2. Since the molecule is neutral, oxygen must be -2 to balance. This follows the general rule that hydrogen is +1 when bonded to nonmetals. More on oxidation states.
What is the oxidation state of sodium in NaCl?
+1
-1
0
+2
Alkali metals, including sodium, always have an oxidation state of +1 in their compounds. In NaCl, chlorine is -1, balancing sodium's +1 charge. This is a fundamental rule in oxidation state assignments. Learn more about alkali metals.
What is the oxidation state of phosphorus in the phosphate ion, PO4 3-?
+5
+3
-3
+1
Oxygen in PO4 3- is -2 each, totaling -8 for four oxygens. The overall charge is -3, so phosphorus must be +5 to reach -3 overall (x + -8 = -3, x = +5). This is a common oxidation state for phosphorus in oxyanions. Phosphate ion details.
What is the oxidation state of sulfur in H2S?
-2
+2
0
+4
Hydrogen is +1 when bonded to nonmetals. In H2S, total from hydrogen is +2, the molecule is neutral, so sulfur must be -2. This follows the standard rule for hydrogen and sulfur bonding. Redox and oxidation states.
What is the oxidation state of hydrogen in HCl?
+1
-1
0
+2
In most compounds, hydrogen has an oxidation state of +1, except in metal hydrides. In HCl, chlorine is -1, balancing hydrogen's +1. This makes the molecule neutral. Hydrogen oxidation states.
What is the oxidation state of oxygen in hydrogen peroxide, H2O2?
-1
-2
0
+1
Peroxides have an O–O bond and each oxygen has an oxidation state of -1. In H2O2, hydrogen is +1 each, totaling +2. The two oxygen atoms at -1 each balance the +2 from hydrogen. More on peroxides.
What is the oxidation state of chlorine in the chlorate ion, ClO3-?
+5
+3
+7
+1
Each oxygen is -2, giving -6 total for three oxygens. The overall charge is -1, so chlorine must be +5 (x + -6 = -1, x = +5). Chlorate commonly has Cl in the +5 state. Chlorate ion details.
What is the oxidation state of nitrogen in nitrogen dioxide, NO2?
+4
+3
+5
-2
Oxygen is -2 each, so two oxygens give -4. The molecule is neutral, so nitrogen must be +4 to balance (-4 + x = 0, x = +4). Nitrogen dioxide is a common example of a +4 oxidation state. NO2 information.
What is the oxidation state of sulfur in the sulfite ion, SO3 2-?
+4
+6
+2
-2
Each oxygen is -2, so three oxygens total -6. The overall charge is -2, so sulfur must be +4 (x + -6 = -2, x = +4). Sulfite commonly features sulfur in the +4 state. Sulfite ion details.
What is the oxidation state of manganese in potassium permanganate, KMnO4?
+7
+6
+4
+2
Oxygen is -2 each, totaling -8 for four oxygens. Potassium is +1. The permanganate ion is neutral overall, so Mn + 1 - 8 = 0, giving Mn = +7. Permanganate is a classic +7 oxidation state. Permanganate ion.
What is the average oxidation state of iron in magnetite, Fe3O4?
+8/3
+2
+3
+5/3
Magnetite contains two Fe3+ ions and one Fe2+ ion per formula unit. The average oxidation state is (2×3 + 1×2)/3 = +8/3. This mixed-valence compound shows both oxidation states in a single structure. Magnetite details.
What is the oxidation state of chromium in the dichromate ion, Cr2O7 2-?
+6
+3
+4
+5
Each oxygen is -2, giving -14 for seven oxygens. The ion has a -2 charge, so 2Cr + (-14) = -2, which yields Cr = +6. Dichromate is a well-known +6 oxidation state for chromium. Dichromate ion.
What is the average oxidation state of sulfur in thiosulfate, S2O3 2-?
+2
+4
+5
+3
In S2O3 2-, three oxygens contribute -6. The overall charge is -2, so the two sulfurs share a total of +4 (2x + -6 = -2 => 2x = +4, x = +2 average). Thiosulfate shows different individual sulfurs but this is the average. Thiosulfate ion.
What is the oxidation state of copper in copper(II) sulfate, CuSO4?
+2
+1
0
+3
Sulfate, SO4 2-, has a -2 charge. In CuSO4, copper combined with sulfate is neutral, so Cu + (-2) = 0, giving Cu = +2. Copper(II) indicates the +2 oxidation state. Copper(II) sulfate.
In the coordination complex [Co(NH3)5Cl]2+, what is the oxidation state of cobalt?
+3
+2
+4
+1
Ammonia is a neutral ligand and chloride is -1. The complex has a +2 overall charge, so Co + (5×0) + (-1) = +2, which gives Co = +3. This is a common oxidation state in cobalt ammine complexes. Coordination chemistry.
0
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Study Outcomes
Understand Oxidation Number Rules -
Apply fundamental guidelines to determine oxidation states of elements in compounds and ionic species.
Assign Oxidation States Accurately -
Use step-by-step strategies to assign oxidation numbers to atoms in real-world compounds during your oxidation number practice.
Identify Exceptions and Special Cases -
Recognize common anomalies such as peroxides and polyatomic ions when conducting oxidation state practice challenges.
Analyze Complex Molecules -
Deconstruct multi-element compounds to calculate and verify oxidation numbers in practice oxidation numbers problems.
Evaluate and Reflect on Performance -
Review quiz results to pinpoint areas for improvement and reinforce your mastering of oxidation number practice problems.
Cheat Sheet
Zero Oxidation State for Pure Elements -
In oxidation state practice, any element in its elemental form has an oxidation number of zero, whether it's O2, N2, or a metal like Fe. This foundational rule comes from IUPAC and is vital for oxidation numbers practice in compounds.
Algebraic Sum Equals Molecular Charge -
When practicing oxidation numbers, the sum of all oxidation states in a neutral molecule equals zero, while in ions it matches the ion's charge. Regular oxidation numbers practice with species like SO42 - or NH4+ reinforces this principle.
Common Oxidation States of Key Elements -
Groups 1 and 2 metals always have +1 and +2 charges, respectively, while fluorine is always −1 in compounds. Recognizing these patterns streamlines assigning oxidation numbers practice and appears across reputable sources like Khan Academy and university chemistry sites.
Oxygen's Versatile Oxidation States -
Oxygen is typically −2, except in peroxides (−1) and in OF2 where it's +2. Practicing oxidation numbers with H2O2 and OF2 helps you master oxygen exceptions.
Mnemonics and Sample Problems -
Use "OIL RIG" ("oxidation is loss, reduction is gain") to keep electron flow straight, then tackle practice oxidation numbers problems on H2SO4 or KMnO4. Regular working through oxidation number practice problems solidifies your skills and reveals areas to revisit.
