The answer is: " NaCl + H₂O " ; (or; write as: " H₂O + NaCl " ) .
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Specifically:
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HCl + NaOH —> NaCl + H₂O ; or; write as:
NaOH + HCl —> H₂O + NaCl .
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This type of "double-replacement" reaction is called "neutralization".
Since we are adding a strong acid to a strong base (reactants), we know that the product will be: 1) a salt ; and 2) water. Since we know one of the reactants will be "water" (H₂O) ; we can find the base (i.e. , the "remaining product") from selecting the "unused elements" to form the corresponding "salt".
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