Formula to find the percent composition of an element in a compound is

.
Now enter the variables into the formula.

%
Round to 3 significant figures. 15.897% = 15.9%
The answer is 15.9% H
Answer:
a. the Kinetic energy of particles is determined by their mass and their velocity.
Answer:
The specific heat of sodium is 1,23J/g°C
Explanation:
Using the atomic weight of sodium (23g/mol) and the atomic weight definition, we have that each mole of the substance has 23 grams of sodium.
starting from this, we use the atomic weight of sodium to convert the units from J / mol ° C to J / g ° C

The balanced equation for the neutralisation reaction is as follows
2H₃PO₄ + 3Mg(OH)₂ --> Mg₃(PO₄)₂ + 6H₂O
stoichiometry of H₃PO₄ to H₂O is 2:6
number of H₃PO₄ moles reacted - 0.24 mol
if 2 mol of H₃PO₄ form 6 mol of H₂O
then 0.24 mol of H₃PO₄ forms - 6/2 x 0.24 = 0.72 mol of H₂O
therefore 0.72 mol of H₂O are formed