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. Matter and Measurements4h 31m
2. Atoms and the Periodic Table5h 23m
3. Ionic Compounds2h 18m
4. Molecular Compounds2h 18m
5. Classification & Balancing of Chemical Reactions3h 17m
6. Chemical Reactions & Quantities2h 27m
7. Energy, Rate and Equilibrium3h 46m
8. Gases, Liquids and Solids3h 25m
9. Solutions4h 10m
10. Acids and Bases3h 29m
11. Nuclear Chemistry56m
BONUS: Lab Techniques and Procedures1h 38m
BONUS: Mathematical Operations and Functions47m
12. Introduction to Organic Chemistry1h 34m
13. Alkenes, Alkynes, and Aromatic Compounds2h 12m
14. Compounds with Oxygen or Sulfur1h 6m
15. Aldehydes and Ketones1h 1m
16. Carboxylic Acids and Their Derivatives1h 11m
17. Amines39m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 41m
21. The Generation of Biochemical Energy2h 8m
22. Carbohydrate Metabolism2h 22m
23. Lipids2h 26m
24. Lipid Metabolism1h 45m
25. Protein and Amino Acid Metabolism1h 37m
26. Nucleic Acids and Protein Synthesis2h 54m

5. Classification & Balancing of Chemical Reactions

Redox Reactions

GOB Chemistry

5. Classification & Balancing of Chemical 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 Cr in Cr2O7^2-, the oxidation state is +6. For N in HNO2, the oxidation state is +3.

Determine the oxidation states of the elements in the products. For Cr in Cr^3+, the oxidation state is +3. For N in NO3^-, the oxidation state is +5.

Compare the oxidation states of each element in the reactants and products to identify changes. A decrease in oxidation state indicates reduction, while an increase indicates oxidation.

Observe that the oxidation state of Cr decreases from +6 in Cr2O7^2- to +3 in Cr^3+, indicating that Cr is being reduced.

Conclude that the element being reduced in the reaction is Chromium (Cr), as its oxidation state decreases during the reaction.