What is the purpose of a buffer?

A buffer solution is a solution made to prevent the pH level of something from changing when you add a base or an acid to it. For example, if you put a buffer solution in a pool, and then you put chlorine in it, the chlorine's effect on the PH level will be suppressed.

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you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6