Answer=1
Potassium Sulfide= K2S (two metals, one non metal)
Sodium Oxide=Na2O (two metals. one nonmetal)
Sodium Chloride=NaCl (one metal, one nonmetal)
Magnesium Oxide=MgO (one metal, one nonmetal)
Magnesium Chloride=MgCl2 (one metal, two nonmetals)
Answer:

Explanation:
Mass of stock solution = 20 g
Molar mass of NaOH = 40 g/mol
Volume of stock solution = 0.150 mL
= Concentration of NaOH for the final solution
= Amount of stock solution taken = 15 mL
= Total volume of solution = 65 mL
Molarity is given by

We have the relation

The concentration of NaOH for the final solution is
.
Answer:
CuSO4 + 2NaOh -> CuOH2 + Na2SO4
Explanation:
The sulphate ion is basically an anion(negatively charged ion) with a charge of overall -2. The hydroxide ion is also an anion with a charge of overall -1. Copper ion is described as copper (II) meaning that it has a charge of +2. Sodium is an alkali metal meaning that it has a charge of +1.
Now we know that the end results are copper hydroxide and sodium sulphate. Since the copper ion has a charge of +2, two hydroxide ions should bond with copper. The sulphate ion has a charge of -2, meaning that two sodium ions should bond with sulphate. There should be two sodium ions to bond with one sulphate ion and two hydroxide ions to bond with one copper ion. Therefore, the coeffiecient for sodium hydroxide should be two.
Total mass of the crystal:
23 x 2 + 32 + 16 x 4 + 10 x 18
= 322
Mass of water:
10 x 18
= 180
Percentage of water = 180 / 322 x 100 = 55.9%