Buffer is composed of weak acid and its conjugate base or weak base and it is conjugate acid. so The correct answer is:
0.21 M hydrofluoric acid + 0.20 M potassium Fluoride
due to the first choice contain NaOH which is strong base not weak
second choice both salts no acid or base
Third choice contain HNO₃ which is considered as strong acid
Fourth choice contain ammonia but without its conjugate acid like (NH₄Cl for example) instead it has different salt
Fifth Choice contain HF which is weak acid and KF which is its conjugate base so this is the correct one
CO is not an element because CO is a Compound. Elements contain One capital and one lowercase letter. While Compounds contain two or more capital letters.
Answer:
The mole is the SI unit for amount of a substance.
Explanation:
Just like the dozen and the gross, it is a name that stands for a number. There are therefore 6.02 × 10 23 water molecules in a mole of water molecules.
Given that acids burns and the reactions of some metals with acids are violent, you have to protect agains spills and splashes that can seriously harm you: your eyes, your hands, your arms, your feet, even your clothe.
So you shall use:
- Safety glasses (googles)
- Chemical gloves
- Lab coat
- Closed shoes