How much does the mass of 12.65-g sample of copper(II) nitrate hexahydrate decrease when heated?
1 answer:
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Explanation:
Using Beer-Lambert's law :
Formula used :
where,
A = absorbance of solution
c = concentration of solution
l = length of the cell
= molar absorptivity of this solution
According to question:
A = (C) : absorbance measured by the spectrometer
c = (B) : concentration, in mol/L, of the stock solution from which the sample was made
l = (A): pathlength of light through the cell
ε = (D) : molar absorptivity, a constant unique to that substance at that wavelength
Answer : The mass of helium gas added must be 12.48 grams.
Explanation : Given,
Mass of helium (He) gas = 6.24 g
Molar mass of helium = 4 g/mole
First we have to calculate the moles of helium gas.
Now we have to calculate the moles of helium gas at doubled volume.
According to the Avogadro's law, the volume of gas is directly proportional to the number of moles of gas at same pressure and temperature. That means,
or,
where,
= initial volume of gas = V
= final volume of gas = 2V
= initial moles of gas = 1.56 mole
= final moles of gas = ?
Now we put all the given values in this formula, we get
Now we have to calculate the mass of helium gas at doubled volume.
Therefore, the mass of helium gas added must be 12.48 grams.