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Name: Sharaybia J.
Status: Parent
Grade: 9-12
Location: SC
Date: May 2008

Question:
As a parent, what should I know about acids and bases? What does an acid do? What does a base do? If you make a reaction, what will come about?



Replies:
Sharaybia,

I am assuming that your question is about safety issues.

The difficulty in trying to answer your question is that there is quite a wide range of acids and bases that a normal child can encounter in the home or elsewhere. Vinegar and fruit juices have acid in them. Antacid tablets and baking soda/baking powder are basic. Most of these substances when used appropriately are benign or even quite helpful.

On the other hand, there may be some products in your house that are acidic or basic and can be quite damaging if in contact with skin/eyes or ingested. Many cleansers are either acidic or basic and can be harmful. The reason such strong or concentrated acids and bases are harmful can come from at least three different issues: (a) they are very good solvents - what makes them good cleansers also makes them dangerous to the skin (which can partially dissolve, cause irritation, or remove oils and dry them), (b) they are very good oxidizers - in essence, can react with parts of the body and convert them to some other substance, (c) they produce quite a bit of heat when they react, and the heat in itself can do damage.

Last, there are many reports of homeowners who think that mixing different cleansers will make them work better. This is dangerous because some cleansers are acids, while others are bases. Not only will mixing such different cleansers make them less effective, they can also produce much heat and gas. Many people have been injured by the heat or gases that are produced in such uninformed decisions.

Greg (Roberto Gregorius)


Hi there

Before we can answer what does an acid do, you need to have some understanding of what an acid IS. Water is H2O (Usually the 2 is written smaller and below the line, but I can't do that in plain text) We could also think of water as an H and an OH - still 2 H's and one O, H being Hydrogen, and O being Oxygen The H takes on a + (positive ) charge, while the OH takes on a - (negative ) charge, because the OH takes an electron from the H. (I hope you are still with me here!) The H+ cause the solution to act as an acid, and the OH- causes it to act as a base(or it can also be called an alkali) In pure water, there will always be the same number of H+'s as OH-'s so water is neutral - neither acid or base.

Some metals are able to take the H away from the water - and turn them into Hydrogen gas. This leaves behind the metal now with a + charge, because it gave an electron to the H+ to make it into hydrogen gas. At the same time, there are a LOT of left over OH- from the water. This means that metals produce bases, which are called Metal Hydroxide, such as Sodium Hydroxide, which is a VERY strong base, and you might use it to clear drains or wash ovens. (And that is because Fat is a weak acid!!!) Many non-metals are able to react with water in such a way that they bind up the OH- and leave a lot of H+ floating around. These solutions will be acidic. Hydrogen Sulfate dissolves in water to produce lots of SO4- and lots of H+ Hydrogen Sulfate is usually called sulphuric acid. Similarly, Hydrogen Chloride can produce lots of H+ (and Cl- ) so HCl is usually called Hydrochloric acid.

Now here is the kicker - when a strong base and a strong acid are allowed to react together (carefully we hope - these reactions can be violent!!) then the result is called a salt. Hydrochloric Acid HCl plus Sodium Hydroxide NaOH produces water and Sodium Chloride - which is common sea salt. In chemical notation we write -

HCl -->H+ + Cl- NaOH --> Na+ + OH-

H+ + Cl- + OH- + Na+ --> HOH + NaCl

( The --> is an arrow and is read as 'forms' )

Sulfuric Acid + Magnesium Hydroxide --> Water and Magnesium Sulfate (Epsom Salts!!)

H2SO4 + Mg(OH)2 --> 2H+ + SO4- + Mg++ + 2 OH- --> 2HOH + MgSO4

(that one is a bit more complicated because there are 2 H+'s and 2 OH-'s )

These things I have mentioned so far are considered STRONG acids and bases, because they produce LOTS of H+'s for acid, or LOTS of OH- for the bases.

There are MANY MANY MANY substances which are able to produce SOME H+'s or a FEW H+'s These are less strong, or weak acids. Vinegar is a medium acid, blood is a weak acid, rain that falls through polluted air is a weak acid, and as mentioned, fats are weak acids (very very weak as it turns out).

Likewise, there are MANY MANY MANY substances which are weak bases - ammonia, spit and limestone (yes the rock) are all weak bases. Acids and bases are chemical opposites, so something that is an acid will react with a base and they will both be neutralised. That is why Sodium Hydroxide is able to dissolve fat, and why acid rain is able to dissolve limestone (You knew there was a reason for putting those in didn't you )

Most substances you come across in normal day to day activities will fall into one category or the other - there are not very many substances that are completely neutral.

I hope this has been a little bit useful, and not too technical, but you have entered into a realm of heavy duty chemistry, and it is very hard to give any explanation without going into details.

By the way - if you react Caustic Soda (Sodium Hydroxide) with a Fat (Tallow or Stearic Acid) you will end up with something called Sodium Tallowate or Sodium Stearate. Have a look at the ingredients list on the side of your soap package, or bottle of handwash and you may well find Sodium Tallowate or Sodium Stearate as one of the ingredients. Sodium Tallowate and Sodium Stearate are soap!!!!

Nigel S
Tennant Creek High School
AUSTRALIA



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