Determine the oxidation number of carbon in CO₃²⁻. Recall that the oxidation number of oxygen is always −2.

• +4

• +2

• +6

• −2

• −4

Name the acid HNO₂.

• nitrous acid

• nitric acid

• sulfuric acid

• hydrochloric acid

• chlorous acid

Assign oxidation numbers to each atom in HNO₂.

• H = +1, N = +3, O = −2

• H = +1, N = +5, O = −2

• H = +2, N = +3, O = −2

• H = +2, N = +5, O = −2

• H = +1, N = +3, O = −1

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

Assign oxidation numbers to each atom in CO₂.

• C = +4, O = −2

• C = +2, O = −2

• C = +3, O = −2

• C = +4, O = −1

• C = +1, O = −2

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

In the reaction Cu(NO₃)₂ + Zn → Cu + Zn(NO₃)₂, which species is reduced?

• NO₃^-

• Zn

• Cu

• Zn(NO₃)₂

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

Assign oxidation numbers to each atom in MnO₄⁻.

• Mn = +7, O = −2

• Mn = +5, O = −2

• Mn = +1, O = −2

• Mn = +3, O = −1

• Mn = −2, O = +2

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

Which of the following statements concerning oxidation-reduction reactions is true?

• Metals tend to form negative ions.

• The oxidation number of the oxidizing agent does not change during redox reactions.

• Non-metals tend to be oxidized.

• Oxidation cannot occur without reduction.

In the reaction 2 Na + Cl₂ → 2 NaCl, ? ​ ​ (a)   is(are) oxidized and ? (b)   is(are) reduced.

• the products; the reactants
• the reactants; the products
• Cl; Na
• Na
• Cl
• NaCl

Answer explanation

Reduction is the gain of electrons and is indicated by the algebraic decrease of the oxidation number. Oxidation is the loss of electrons and is indicated by the algebraic increase of the oxidation number. 

Oxidation numbers are per atom. The oxidation number of free, uncombined elements is zero.

In the redox reaction CrO₃ + 3 H₂ → Cr + 3 H₂O, what is happening to Cr?

• Cr is being reduced from +6 to 0.

• Cr is being oxidized from +6 to 0.

• Cr is being oxidized from 0 to +6.

• Cr is being reduced from 0 to +6.

• The correct answer is not given.

Tags

NGSS.HS-PS1-2

When C₃H₈ is burned in oxygen, the products are

• CO₂ and H₂O

• C and H₂.

• CH₂ and H₂O.

• CO₂ and H₂.