This is a bit too broad. Maybe this is something to google up
The neutral pH is 7. Less than 7 indicates an acid and more than 7 indicates a base (up to 14).
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NaCl - it's a salt (we can't measure the pH)
H2O - it can be an acid but also a base (the pH it is almost neutral,meaning close to 7 )
HF - it is a strong acid
</span><span>
KOH
- it is a strong base (pH=14)
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↓
He needs to use HF (Hydrogen fluoride) to decrease the pH.
There are no more courts of appeal within the state system.
