How much heat must be removed from 357 g of water at 76.9C in order to cool it down to 18.1C?
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Answer : The chemical formula of a compound is,
Solution : Given,
Mass of gallium = 1.25 g
Mass of gallium oxide = 1.68 g
Mass of oxygen = Mass of gallium oxide - Mass of gallium
Mass of oxygen = 1.68 - 1.25 = 0.43 g
Molar mass of Ga = 69.72 g/mole
Molar mass of O = 16 g/mole
Step 1 : convert given masses into moles.
Moles of Ga =
Moles of O =
Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.
For Ga =
For O =
The ratio of Ga : O = 1 : 1.5
To make in whole number we multiple ratio by 2, we get:
The ratio of Ga : O = 2 : 3
The mole ratio of the element is represented by subscripts in empirical formula.
The Empirical formula =
The empirical formula weight = 2(69.72) + 3(16) = 187.44 gram/eq
Now we have to calculate the molecular formula of the compound.
Formula used :
Molecular formula =
Therefore, the chemical of the compound is,