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MDCAT
Chemistry
2019

Chemistry · Electrochemistry

Work through this past-paper style MCQ, then read the full explanation. Practice more chemistry questions on mMCQ with adaptive practice and topic analytics.

Question

The oxidation states of Nitrogen in NH4NO3 are:

Options
  • A

    -3 and +5

  • B

    +5 and -3

  • C

    -3 & -3

  • D

    Zero

Explanation

In NH₄NO₃, nitrogen is present in two different ions: NH₄⁺ and NO₃⁻. For NH₄⁺, the sum of oxidation states is +1. Since each hydrogen has an oxidation state of +1, the nitrogen must have an oxidation state of -3 to balance it (+1 = -3 + 4). For NO₃⁻, the sum of oxidation states is -1. Oxygen typically has an oxidation state of -2, so the nitrogen must be +5 to account for the charge (-1 = +5 - 6). Therefore, the correct oxidation states of nitrogen in NH₄NO₃ are -3 in NH₄⁺ and +5 in NO₃⁻.

NH₄⁺

N + 4 = 1

N = 1-4

N = -3

NO3-

N + 3(-2)= -1

N - 6 = -1

N = -1 + 6

N= 5

Incorrect. While these are the correct oxidation states, their order does not correspond to the arrangement of NH₄⁺ and NO₃⁻ in NH₄NO₃.

Incorrect. This suggests that nitrogen has an oxidation state of -3 in both ions, which is not the case in NH₄NO₃.

Incorrect. The compound NH₄NO₃ consists of ions with different oxidation states; therefore, the oxidation states of nitrogen cannot both be zero.

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Tagged under Chemistry · Electrochemistry · 2019