0.702g arsenic combines with 0.225g of oxygen to make an oxide of arsenic. When heated this produces a gas with a volume of 52cm3.
How do i work out the molecular formula of the oxide when its in a gaseous state?
The weight ratio will tell you, after dividing by atomic weights of AS and O, that the ratio of As to O is 2 to 3. That means the formula for the oxide is
As2O3 or some multiple.
Knowing the volume of the product does not help unless you also know the pressure and temperature. If it is STP (273 K and 1 atm), you would have .052 liter/22.4 liters/mole = 2.32*10^-3 moles weighing 0.702 + 0.225 = 0.927 g. That is 400 g/mole. That would tend to imply a vapor formula of As4O6.
Thnk you so much
To work out the molecular formula of the oxide in its gaseous state, we need to consider the weight ratio of arsenic (As) to oxygen (O) in the compound.
Given that 0.702g of arsenic combines with 0.225g of oxygen, we can find the weight ratio. The atomic weight of arsenic is approximately 74.92 g/mol, and the atomic weight of oxygen is approximately 16.00 g/mol.
So, the weight ratio of As to O can be found by dividing the weight of arsenic by its atomic weight, and dividing the weight of oxygen by its atomic weight:
0.702g As / 74.92 g/mol As ≈ 0.00936 mol As
0.225g O / 16.00 g/mol O ≈ 0.01406 mol O
Now, by dividing the moles of As and O by the smaller value (0.00936mol), we can find the ratio of As to O:
0.00936 mol As / 0.00936 mol As ≈ 1
0.01406 mol O / 0.00936 mol As ≈ 1.5
The ratio of As to O is approximately 1:1.5, which can be simplified to 2:3. This tells us that the formula for the oxide is As2O3 or some multiple thereof.
However, the volume of the gas (52cm3) mentioned in the question is not sufficient to determine the molecular formula of the oxide. The volume alone doesn't provide enough information unless the pressure and temperature are known. For example, if the conditions are standard temperature and pressure (STP), which is 273 K and 1 atm, we can calculate the number of moles by dividing the volume by the molar volume (22.4 liters/mol).
In this case, the calculation would be:
52 cm3 / 1000 cm3/liter = 0.052 liter
0.052 liter / 22.4 liters/mol = 2.32 x 10^-3 mol
Additionally, we know the total weight of the compound is 0.702g + 0.225g = 0.927g.
Assuming the compound is As2O3, its molar weight is approximately 400 g/mol. By dividing the total weight by the molar weight, we can obtain the number of moles:
0.927g / 400 g/mol ≈ 0.00232 mol
Comparing the calculated moles (0.00232 mol) with the moles calculated from the volume (2.32 x 10^-3 mol), we can see that they are approximately equal. This suggests that the molecular formula of the oxide would be As4O6.
Overall, without additional information about the pressure and temperature, we can conclude that the oxide could have a molecular formula of As2O3 or As4O6, depending on the conditions.