Oxidation numbers of X, Y, Z are +6, -2 and -1 respectively. Possible molecular formula when atoms combine:
Correct answer: B. XY2Z2
- A. X2YZ
- B. XY2Z2
- C. XYZ2
- D. XY2Z
Explanation
A neutral compound must have oxidation numbers summing to zero, and XY2Z2 gives plus 6, then two at minus 2 and two at minus 1, that is 6 minus 4 minus 2, which is exactly zero. Testing each option the same way disposes of the others: XYZ2 gives 6 minus 2 minus 2, which is plus 2 rather than zero. Summing to zero is the only test needed for a neutral formula.
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About Oxidation and Reduction
Oxidation involves loss of electrons, increase in oxidation number or addition of oxygen, while reduction involves electron gain, decrease in oxidation number or removal of oxygen. The topic covers oxidising and reducing agents, oxidation-number changes, redox equations and the distinction between oxidation at the anode and reduction at the cathode.
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