1. Which of the following is sulfurous acid? A. H2SO4, B. H2SO3, C. H2S
QUESTION:
Which of the following is sulfurous acid? A. H2SO4, B. H2SO3, C. H2S
Acids produce H+ when dissolved in water.
H2SO4  2 H+ + SO42-
H2SO3  2 H+ + SO32-
H2S  2 H+ + S2-
The name of an acid is related to the name of anion produced once the hydrogen ions are removed.
Which of the following is sulfurous acid? A. H2SO4, B. H2SO3, C. H2S
PAUSE CLICK
Acids are compounds that produce hydrogen ions in water.
CLICK
For example, for the acid given in choice A, …H2SO4, …. Up to 2 hydrogen ions
HIGHLIGHT 2 H+
can break off from the molecule when the compound is placed in water.
When the 2 hydrogen ions break off, what is left is a sulfate ion…. SO4 with a –2 charge.
CALLOUT “sulfate” pointing to SO42-
Similarly, H2SO3 has 2 hydrogen atoms that can break off as hydrogen ions, leaving behind a sulfite ion,… SO3 with a –2 charge
CALLOUT “sulfite” pointing to SO32-
CLICK And, H2S has 2 hydrogen atoms that can break off as hydrogen ions, leaving behind a sulfite ion,… SO3 with a –2 charge
CALLOUT “sulfide” pointing to S2-
PAUSE
The name of an acid is related to the name of the anion produced once the hydrogen ions are removed.
CLICK CONTINUED ON NEXT SLIDE

2. So, the formula of hypochlorous acid is HClO
If the name of the acid is hydro-----ic acid, the name of the anion left behind when H+ ions are removed ends in ide.
Ex.: hydrochloric acid yields hydrogen and chloride ions
Since chloride is Cl-, hydrochloric acid is HCl
If the name of the acid is -----ic acid, the name of the anion left behind when H+ ions are removed ends in ate.
Ex.: carbonic acid yields hydrogen and carbonate ions
Since carbonate is CO32-, carbonic acid is H2CO3
If the name of the acid is -----ous acid, the name of the anion left behind when H+ ions are removed ends in ite.
Ex.: hypochlorous acid yields hydrogen and hypochlorite ions
Since hypochlorite is ClO-, hypochlorous acid is HClO
In general,
If the name of the acid starts with hydro
HIGHLIGHT
and ends with ic acid,
HIGHLIGHT the name of the anion left behind when H+ ions are removed ends in ide.
For example, the anion left behind when hydrogen ions break off from hydrochloric acid is chloride
Since chloride is Cl with a –1 charge, one hydrogen ion must have broken off from hydrochloric acid to produce a chloride ion.
So the formula of hydrochloric acid is HCl.
If the name of the acid does not start with hydro, but ends in ic acid, the name of the anion left behind when H+ ions are removed ends in ate.
For example, carbonic acid does not start with hydro,
CALLOUT “no hydro”
but it ends in ic acid.
Therefore, the anion left behind when hydrogen ions break off from carbonic acid is carbonate.
Carbonate is CO3 with a –2 charge. The –2 charge means that the molecule it came from must have produced two hydrogen ions.
So the formula of carbonic acid is H2CO3.
Finally, if the name of the acid ends in ous acid,
HIGHLIGHT ous acid
Then the name of the anion left behind when H+ ions are removed ends in ite.
HIGHLIGHT ite
Therefore, hypochlorous acid breaks up into hydrogen and hypochlorite ions.
Hypochlorite is ClO with a –1 charge. The –1 charge means that the molecule it came from must have produced one hydrogen ion.
So, the formula of hypochlorous acid is HClO
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3. QUESTION:
Which of the following is correct formula for sulfurous acid? A. H2SO4, B. H2SO3, C. H2S
The “ous” in sulfurous acid means that the anion left behind when the H+ ions are removed is sulfite.
Sulfite is SO32-
Sulfurous acid is H2SO3
Removal of all H+ from H2SO4 gives us SO42-, or sulfate. Therefore, H2SO4 is sulfuric acid.
Removal of all H+ from H2S gives us S2-, or sulfide.
Therefore, H2S is hydrosulfuric acid.
CLICK The “ous” in sulfurous acid means that the anion left behind when the hydrogen ions break off from the molecule is sulfite.
CLICK The formula for sulfite is SO3 with a –2 charge.
Since a molecule of sulfurous acid is neutral, the molecule must have lost 2 hydrogen ions.
The charge of two hydrogen ions, 2 times (+1)
HIGHLIGHT and one sulfite ion
HIGHLIGHT –2 in formula of sulfite
add up to a zero.
Therefore the formula of sulfurous acid is H2SO3.
The correct answer is choice B.
Let’s examine choices A and C.
CLICK
If we were to remove two hydrogen ions from H2SO4, we would end up with SO4 with a –2 charge.
SO4 with a –2 charge is called sulfate. Therefore, H2SO4 is sulfuric acid.
How about choice C. If we were to remove two hydrogen ions from H2S, we would end up with S with a –2 charge.
S with a –2 charge is sulfide. Therefore, H2S is hydrosulfuric acid.

4. Video ID: © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08