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pui

2016-02-07 2:40 am

1. What is the coefficient of M when the following equation is completed and balanced if M is an alkali metal?
M (s) +H2O (l)->

2.Oxides of most nonmetals combine with water to from ______.

3. Among the hydrogen halides, only ____is a weak acid.

4. The only noble gas that does not have the ns2np6 valence electron configuration is ______.

5. The first ionization energies of the elements _____ as you go from left to right across a period of the periodic table, and _____ as you go from the bottom to the top of a group in the table.

回答 (1)

己式庚辛

2016-02-08 3:30 pm

✔ 最佳答案

1.
If M is an alkali metal, it reacts with water to give M+ ion. MOH & H2 is formed.
Write down the reactants & products first:
a M + b H2O ------> c MOH + d H2
where a, b, c, d are integers.
a = c due to conservation of no. of atoms of M
b = c due to conservation of no. of atoms of O
2b = c + 2d due to conservation of atoms of H

2M + 2H2O ------> 2MOH + H2

2.
acid. e.g.
Carbon dioxide to give Carbonic acid
Sulfur dioxide & Sulfur trioxide to give Sulfurous acid & Sulfuric acid, respectively
Nitrogen dioxide to give Nitrous acid & Nitric acid
Phosphorous pentoxide to give Phosphoric acid

3.
Hydrogen fluoride (HF)
due to the strong bond between hydrogen & fluorine

4.
helium. Obvious.

5.
increase; decreases
look at the change in effective nuclear charge

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