Answer:
Both are equal
Explanation:
Mass of starting material i.e Aluminium is
grams
The weight of oxygen is 
There are 4 atoms of aluminium and 3 atoms of oxygen
Thus, the total mass of starting material is
mass of one atom of aluminium
mass of one atom of oxygen

grams
Mass of new substance is also equal to
mass of one atom of aluminium
mass of one atom of oxygen

grams
Molality= mol/ Kg
if we assume that we have 1 kg of water, we have 3.19 moles of solute.
the formula for mole fraction --> mole fraction= mol of solule/ mol of solution
1) if we have 1 kg of water which is same as 1000 grams of water.
2) we need to convert grams to moles using the molar mass of water
molar mass of H₂O= (2 x 1.01) + 16.0 = 18.02 g/mol
1000 g (1 mol/ 18.02 grams)= 55.5 mol
3) mole of solution= 55.5 moles + 3.19 moles= 58.7 moles of solution
4) mole fraction= 3.19 / 58.7= 0.0543
<u>Answer:</u> The given sample of water is not safe for drinking.
<u>Explanation:</u>
We are given:
Concentration of fluorine in water recommended = 4.00 ppm
ppm is the amount of solute (in milligrams) present in kilogram of a solvent. It is also known as parts-per million.
To calculate the ppm of fluorine in water, we use the equation:

Both the masses are in grams.
We are given:
Mass of fluorine =
(Conversion factor: 1 g = 1000 mg)
Mass of water = 5.00 g
Putting values in above equation, we get:

As, the calculated concentration is greater than the recommended concentration. So, the given sample of water is not safe for drinking.
Hence, the given sample of water is not safe for drinking.
About 1.051 moles (depends on how u round it)
The number of molecules of oxygen in the cylinder is 6.02×1023 molecules
Data obtained from the question
Number of mole of oxygen = 1 mole
Number of molecule of oxygen =?
From Avogadro's hypothesis, we understood that 1 mole of any substance contains 6.02×1023 molecules. This implies that 1 mole of oxygen contains 6.02×1023 molecules.
Since the cylinder contains 1 mole of oxygen, then the number of molecules of oxygen present in the cylinder is 6.02×1023 molecules.