The Strength of Oxyacids


Hey, guys! In this new video, we’re going to take a
look at how do we determine the strength of oxyacids. Up to this point, hopefully you guys know
the difference between binary acids and oxyacids. It’s not only important to be able to identify
them. It’s also important to know if they’re
weak or they’re strong. Because again, a strong acid doesn’t need
an ICE chart in order to find pH. A weak acid on the other hand, does require
an ICE chart in order to figure out pH. It’s imperative that you guys, not only
know how to identify things as either binary or oxy but be able to identify them as weak
or strong. Let’s take a look at oxyacids.We’re going
to say here, the strength of oxyacids is based on two major factors. First, it’s based on the number of oxygens
present. And secondly, it’s based on the electronegativity
of the non-metal. Now remember, an oxyacid has H, an oxygen
and a non-metal. Those are the three factors that give us an
oxyacid. Now, we’re going to say the number one rule
when it comes to them—really the only rule. If my oxyacid has 2 or more oxygens than hydrogens
then my oxyacid is a strong acid. You always want a minimum of two more oxygens
than hydrogens. If you don’t have that minimum, then you
won’t be a strong oxyacid. And let’s see how this works out when we
work out the Math for these following three oxyacids.The first compound, we know it’s
an oxyacid because it has H, oxygen and a non-metal. Let’s do the Math. We have three oxygens, we have one hydrogen. What do we have left? We have two oxygens left. When we do this Math, we have a minimum of
two oxygens left. If we don’t have that minimum, then we can’t
be a strong oxyacid. We’ve met the minimum so this a strong oxyacid. Next, the next compound also is an oxyacid
because it has Hs, non-metals, oxygen. The three features of an oxyacid. Let’s do the Math. We have one oxygen. We have six hydrogens. So we actually have an excess of hydrogen
left. We need a minimum of two oxygens left, so
this is definitely weak. And remember, this could not be a base. OH does not make something a base. OH is only a base if it’s connected to metals. Since carbon and hydrogens are not metals,
this could not possibly be a base. Just remember, just because it has OH doesn’t
mean it’s a base. You have to see what is that OH connected
to. Is it connected to metals? If so, then it’s a base. If it’s connected to non-metals, then it’ll
actually be an oxyacid. Finally, the last one. Here we have HBrO4. We have four oxygens. We have one hydrogen. We have three oxygens left. We need a minimum of two left in order for
it to be strong, so this is definitely strong. It’s a simple rule to follow, guys. The book doesn’t say it directly. Most professors never teach it. It’s just something that’s understood
by the Chemistry community. This is the basic rule that we use in order
to determine if an oxyacid is weak or strong.

4 Replies to “The Strength of Oxyacids”

  1. What if you have the same number of X and Oxygen but….. one of them has more Hydrogen in the other???
    For example: H2XO4 VS HXO4? which one is stronger ?

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