1. Arrange each group of compounds/ions in order of increasing pH. Can you also
ID: 801301 • Letter: 1
Question
1. Arrange each group of compounds/ions in order of increasing pH. Can you also briefly explain why.
a) (3 pts) H2SeO3...... H2SeO4 ..... H2SO3 ..... H2SO4......
b) (3 pts) PH2- ......... HS- ........... NH2- ......... Cl-....
c) (3 pts) HIO3 ........ HIO ........ HClO2 ......... HClO3...........
d) (3 pts) Na2CO3 .......... HI ............ CaI2 ............. NH4K..............
e) (3 pts) NH3 H2O OH- H2S
Explanation / Answer
Ans A and Ans C:
The acidic properties of oxyacids of the same element which is in different oxidation states increases with increase in oxidation number.
H2SO3 < H2SO4 ( Acidity)
The acidic properties of the oxyacids of different elements which are in the same oxidation state decreases as the atomic number increases. This is due to increase in size and decrease in electronegativity.
H2SO3 > H2SeO3
Therefore we have for increasing pH as:
H2SeO3>H2SeO4>H2SO3>H2SO4
HIO>HIO3>HCLO>HCLO3
Ans B: Hydrides of V group elements (NH3, PH3, AsH3, SbH3, BiH3) show basic character which decreases due to increase in size and decrease in electronegativity from N to Bi. There is a decrease in electron density in, sp3 -hybrid orbital and thus electron donor capacity decreases. And hence the conjugates shows the opposite effect !! Therefore the most basic is
PH2- > NH2- > HS-> Cl-
Ans D: The order must be
Na2CO3 > NH4K> CaI2 > HI
Because H2Co3 is a weak acid , therefore its salt is a strong base and NH3 is a strong base and hence it salt is a weak acid and hence its solution must be more basic than CaI2.
Ans E:Hydracids of VI group elements (H20, H2S, H2Se, H2Te) act as weak acids. The strength increases in the order H20 < H2S.
The increase in acidic properties is supported by the succes
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