Oxidation States of Arsenic Compounds

This video tutorial explains how to find the oxidation number for arsenic in H3AsO3, also known as arenus acid. It begins by establishing that the compound is neutral, meaning the oxidation numbers sum to zero. The video demonstrates two methods: the first involves assigning known oxidation numbers to hydrogen and oxygen, then solving for arsenic. The second method treats AsO3 as the arenite ion with a charge of -3, leading to the same result. Both methods conclude that arsenic has an oxidation number of +3.

What is the overall charge of the compound H3AsO3?

• Neutral

• Negative

• Positive

• Variable

What is the oxidation state of hydrogen in most compounds?

• -1

• +1

• 0

• +2

In the first method, what is the oxidation state of oxygen assumed to be?

• -2

• +1

• -1

• +2

How is the oxidation number of arsenic determined in the first method?

• By assuming arsenic is neutral

• By balancing the known oxidation states of hydrogen and oxygen

• By using the charge of the arenite ion

• By assuming arsenic is a noble gas

What is the charge of the arenite ion (AsO3) used in the second method?

• 2-

• 3-

• 2+

• 3+

In the second method, what is the oxidation state of oxygen considered to be?

• -2

• +1

• +2

• 0

What is the final oxidation number of arsenic in H3AsO3 as determined by both methods?

• -3

• 0

• +3

• +5

Which of the following statements is true about the methods used to find the oxidation number of arsenic?

• Both methods confirm the same oxidation number

• The second method is incorrect

• Both methods give different results

• The first method is more accurate