Reduction is the A) loss of mass. B) loss of protons. C) gain of protons. 0) los
ID: 990294 • Letter: R
Question
Reduction is the A) loss of mass. B) loss of protons. C) gain of protons. 0) loss of electrons. E) gain of electrons. 2. Glancing at a periodic table, where do you expect to find elements that are good oxidizing agents? A) in the top left B) in the transition metals C) at the bottom left D) on the right (except lor the last group) E) at the bottom 3. When hydrogen reacts with a metal to form a hydride (e.g., CaH2>, what are the oxidation numbers of the calcium (in this case) and hydrogen, respectively, in the product? A) +2 and -1 B) -2 and +1 C) +1 and -2 D) 0 and 0 E) +2 and -2Explanation / Answer
1. Reduction is the E) gain of electrons.
[According to the electronic theory of oxidation and redcution, reduction is such a chemical rection where gaining of electron occurs and in oxidation loss of electron occurs. For example, Fe3+ + e- = Fe2+ ; this is reduction reaction because one electron is gained by Fe3+. On the otherhand, when sodium metal leaves one electron produces sodium ion, Na = Na+ + e- ; this is oxidation reaction because loss of electron occur by sodium]
2. D) on the right (except for the last group).
[The good oxidizing elements are those who can accept electrons very easily. In the periodic table, the elements who are on the left they are very electropositive because they easily can leave their outermost electron. The cause for this is that if they leave their outermost electron now they can achieve the inert gas electronic configuration. Therefore, the first group elements are very electropositive and good reducing agent.
In the periodic table, moving from the left to right the electropositive character decreases i.e. reducing character decreases and oxidizing character increases. In this way, the elements on the right (except inert gas elements group) are less electropositive and most electronegative. So they can easily accept extra electron in their outermost orbit. This is because, after gaining electron they attain the nearest inert gas element's like electronic configuration.]
3. A) +2 and -1.
In the case of CaH2, the Ca is more electropositive than H atom. So, if this compound ionises then they form Ca2+ ion and two H- ions. That is two electrons are removing from one Ca atom, therefore the oxidation number of Calcium is +2. Whereas, these two electrons are gaining by two H atom. Hence, the oxidation number of Hydrogen is (-2/2 = -1) -1.
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