Which element is being reduced in the following reaction? Cr 2 O 7 2- + 3 HNO 2 + 5 H + → 2 Cr 3+ + 3NO 3 - + 4 H 2 O

Here in this practice question it says, which element is being reduced in the following reaction? Alright. So what we're gonna do first is let's tackle the ions that we see. Because remember, if you see an ion, so a single element with a charge, we know that that charge is connected to its oxidation number. Here, h plus 1, its charge is plus 1, so its oxidation number is plus 1. Chromium here is 3 plus, so its oxidation number is plus 3. Next, what we need to do is we need to see what the oxidation numbers are for all the other elements. We're looking to see what's been reduced, which means we need to see which element has had its oxidation number decrease. Alright. So chromium, we don't have a specific oxidation rule for chromium. So chromium is x. Oxygen here is not a peroxide or a superoxide, so its oxidation number would be minus 2. Hydrogen here is with nonmetals so it's plus 1. Nitrogen, we don't have a specific oxidation number rule for it either so it's going to be x. So we'll go back and solve for those x variables later. Next we have oxygen here which is not a peroxide or a superoxide, so its oxidation number is minus 2. Again, nitrogen would be x. Oxygen would be minus 2 here. Hydrogen is with a nonmetal oxygen so it's plus 1. Oxygen is not a peroxide or a superoxide so it's minus 2. So we know that we need to determine what this these x variables are for chromium and nitrogen respectively to see which one had its oxidation number increased or decreased. So for chromium, here we'd say that there's 2 chromiums, so that's 2x, plus 7 oxygen. Each one is minus 2, equals the charge of the compound, which is minus 2. 2x minus 14 equals minus 2. Add 14 to both sides, so 2 x equals plus 12. When you divide by 2 you see that x equals plus 6. So at this point what do we what do we notice? We noticed here that chromium within dichromate was plus 6, and as a product it went down to plus 3. So we see that the oxidation number decreased. So we don't need to go any further. We can say that we know for sure that chromium was the element that was reduced because it went from oxidation number of plus 6 to just plus 3.

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1. Intro to General Chemistry3h 48m
2. Atoms & Elements4h 16m
3. Chemical Reactions4h 10m
4. BONUS: Lab Techniques and Procedures1h 38m
5. BONUS: Mathematical Operations and Functions48m
6. Chemical Quantities & Aqueous Reactions3h 53m
7. Gases3h 49m
8. Thermochemistry2h 37m
9. Quantum Mechanics2h 58m
10. Periodic Properties of the Elements3h 9m
11. Bonding & Molecular Structure3h 29m
12. Molecular Shapes & Valence Bond Theory1h 57m
13. Liquids, Solids & Intermolecular Forces2h 23m
14. Solutions3h 1m
15. Chemical Kinetics2h 53m
16. Chemical Equilibrium2h 29m
17. Acid and Base Equilibrium5h 1m
18. Aqueous Equilibrium4h 47m
19. Chemical Thermodynamics1h 50m
20. Electrochemistry2h 42m
21. Nuclear Chemistry2h 36m
22. Organic Chemistry5h 7m
23. Chemistry of the Nonmetals2h 39m
24. Transition Metals and Coordination Compounds3h 16m

6. Chemical Quantities & Aqueous Reactions

Redox Reactions

General Chemistry

6. Chemical Quantities & Aqueous Reactions

Redox Reactions

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Multiple Choice

Which element is being reduced in the following reaction?
Cr₂O₇^2- + 3 HNO₂ + 5 H⁺→ 2 Cr³⁺ + 3NO₃^- + 4 H₂O

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Identify the oxidation states of each element in the reactants and products. For example, in \( \text{Cr}_2\text{O}_7^{2-} \), chromium (Cr) has an oxidation state of +6, and in \( \text{Cr}^{3+} \), it is +3.

Determine the change in oxidation states for each element. A decrease in oxidation state indicates reduction, while an increase indicates oxidation.

For chromium (Cr), the oxidation state changes from +6 in \( \text{Cr}_2\text{O}_7^{2-} \) to +3 in \( \text{Cr}^{3+} \), indicating a reduction.

Check the oxidation states of other elements: nitrogen (N) in \( \text{HNO}_2 \) changes from +3 to +5 in \( \text{NO}_3^- \), indicating oxidation.

Conclude that the element being reduced is chromium (Cr), as its oxidation state decreases from +6 to +3.

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Which element is being reduced in the following reaction? Cr2O72- + 3 HNO2 + 5 H+ → 2 Cr3+ + 3NO3- + 4 H2O

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Redox Reactions practice set

Which element is being reduced in the following reaction?
Cr₂O₇^2- + 3 HNO₂ + 5 H⁺→ 2 Cr³⁺ + 3NO₃^- + 4 H₂O