To solve number 18 you have to add the positive and negative to equal zero. For example for 18a it would be K2S ( the 2 is a subscript ) because you need 2 positives to cancel out the 2 negatives.
Answer:
is a single replacement reaction.
Explanation:
A chemical reaction in which one element of a compound is replaced by another element is called single replacement reaction.
For example, ![CF_{4} + 2Br_{2} \rightarrow CBr_{4} + 2F_{2}](https://tex.z-dn.net/?f=CF_%7B4%7D%20%2B%202Br_%7B2%7D%20%5Crightarrow%20CBr_%7B4%7D%20%2B%202F_%7B2%7D)
Here, fluorine element in the compound
is replaced by the element bromine.
Therefore, it is a single replacement reaction.
Thus, we can conclude that
is a single replacement reaction.
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The answer to your problem would b b