Oxidation Numbers and Charges

The video tutorial explains how to determine the oxidation number of chromium in calcium dichromate (CaCr2O7). It starts by noting that the compound is neutral, meaning the sum of oxidation numbers is zero. Calcium, being in group two, has a +2 oxidation number. Chromium, a transition metal, is unknown and represented as x. Oxygen is typically -2. An equation is set up: 2 + 2x - 14 = 0, which simplifies to x = +6. Thus, each chromium atom has an oxidation number of +6. The video also mentions the dichromate ion's 2- charge and concludes with a note on alternative methods to find the oxidation number.

What is the overall charge of the calcium dichromate compound?

• Positive

• Negative

• Neutral

• Variable

What is the oxidation number of calcium in calcium dichromate?

• +1

• +2

• 0

• -2

What is the typical oxidation number assigned to oxygen in compounds?

• 0

• -2

• +2

• -1

In the equation 2 + 2x - 14 = 0, what does x represent?

• Oxidation number of calcium

• Oxidation number of oxygen

• Oxidation number of chromium

• Total charge of the compound

What is the oxidation number of chromium in CaCr2O7?

• -6

• +6

• +2

• +3

What is the charge of the dichromate ion (Cr2O7)?

• 1+

• 2-

• 2+

• 1-

Which method is suggested as easier for finding the oxidation number of chromium?

• Using the atomic mass

• Using the charge of the dichromate ion

• Using the periodic table

• Using the compound's neutrality

What is the role of Dr. B in the video?

• Demonstrating a chemical reaction

• Discussing ionic bonds

• Explaining the periodic table

• Calculating oxidation numbers