Why must we always add a concentrated acid to water, slowly and with stirring, and never water to…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
- Why must we always add a concentrated acid to water, slowly and with stirring, and never water to the acid?
- Why can a thin glass beaker crack if this is done wrongly?
Need a reminder? The key ideaShow
Acids give ions (as ) in water; alkalis give ions. Without water there are no ions. Strong acids split fully, weak acids only a little. Always add acid to water, slowly, never water to acid.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Mixing gives out a great deal of heat. If a little water is poured into a lot of acid, it boils at once and splashes hot acid out. Adding acid slowly to plenty of water spreads the heat.
Step 2. (b) The sudden heat in one place makes the glass expand unevenly, so it can crack.
Answer: as above.
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