The reaction between potassium metal and water produces potassium hydroxide and hydrogen gas. the correct equation for this reaction is:

A: K + H2O—> KOH + H2
B: K + H2O—>KOH + H
C: 4K + 3H2O—> 4KOH + 2H
D: 2K + 2 H2O—> 2KOH + H2

2K   +   2H₂O   →   2KOH  + H₂

Explanation:

The reactants are:

    Potassium metal  = K

    Water  = H₂O

 The products are:

  Potassium hydroxide  = KOH

  Hydrogen gas  = H₂  

The reaction equation is given as;  

                Reactants   →   Products

        2K   +   2H₂O   →   2KOH  + H₂

The reaction is a single displacement reaction

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%