A student prepares a solution by dissolving 1.000 mol of Na2SO4 in water. She accidentally leaves the container uncovered and comes back the next week to find only a white, solid residue. The mass of the residue is 322.2 g. Determine the chemical formula of this residue.

Formula is NA2SO4•10H2O

Sodium sulfate decahydrate.

Explanation:

Sodium sulfate is soluble in water. Soduim sulphare form various hydrates, so if the solution is open to the atmosphere for a week at least a lot of the water will have evaporated leaving behind a solid hydrate of Soduim sulfate.

Mass of anhydrous Na2SO4 = molar mass * number of moles

Molar mass = (23*2) + (32*1) + (16*4)

= 146 g/mol

Mass = 146*1

= 146 g of NA2SO4

NA2SO4•nH2O --> Na2SO4 + nH2O

Molar mass of hydrate, NA2SO4.nH2O

= (142 + 18n) g/mol

Mass of NA2SO4.nH2O = (142 + 18n)*1

= (142 + 18n) g

Mass of the residue = 322.2 g

Therefore, 142 + 18n = 322.2

18n = 180.2

n = 10

Formula is NA2SO4•10H2O

Sodium sulfate decahydrate.

0.0588 mol MgSO4 / 0.0588 = 1 mol MgSO4

0.412 mol H2O / 0.0588 = 7 mol H2O

Formula is MgSO4•7H2O

in chemistry, adhesion and cohesion are attractive forces that exist between molecules. they hold the molecules together from each other. they are different in that adhesive force exists between molecules of different substance while cohesive force happens between molecules of same substance.

adhesion between water and glass causes water molecules at the edge of water and glass interface to climb up the wall in a narrow glass tube. this is called capillary action. cohesion is what gives glass its shape and causes water to form a droplet.

2b2t

explanation:

2b2t