4Na + O₂ → 2Na₂O                 Combination
NaOH + HBrO → NaBrO + H₂O       Acid-base
CuSO₄ + ZnCrO₄ → ZnSO₄ + CuCrO₄  Double replacement
KOH + HClO₄ → KClO₄ + H₂O        Acid-base reaction
Explanation:
1.       4Na + Oâ‚‚ → 2Naâ‚‚O    is a combination reaction; Â
 In a combination reaction, there is a formation of a single product from two or more reactants.
2.  NaOH + HBrO → NaBrO + H₂O       Acid-base reaction
  KOH + HClO₄ → KClO₄ + H₂O        Acid-base reaction
In an acid-base reaction, a base combines with an acid to produce salt and water. From the above, one can see how the acids combine with the base to yield a product of salt and water.
3.  CuSO₄ + ZnCrO₄ → ZnSO₄ + CuCrO₄  Double replacement
 This is a double replacement reaction in which there is an actual exchange of partners to form new compounds.
Learn more;
Combination reaction https://brainly.com/question/2364359
precipitation reaction https://brainly.com/question/5464325
neutralization reaction https://brainly.com/question/3243813
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