Answer
Avogadro's number: One mole of any substance contains 6.022×10²³ molecules
Explanation
While finding the number of moles of oxygen molecules present in 3.65 moles of Na2SO4 the conversion factor used would be Avodagro's number, which is
One mole of any substance contains 6.022×10²³ molecules.
atomic mass=percentage of isotope a * mass of isotope a + percentage of isotope b * mass of isotope b+...+percentage of isotope n * mass of isotope n.
Data:
mass of isotope₁=267.8 u
percentage of isotope₁=90.3%
mass of isotope₂=270.9 u
percentage of isotope₂=9.7%
Therefore:
atomic mass=(0.903)(267.8 u)+(0.097)(270.9 u)=
=241.8234 u + 26.2773 u≈268.1 u
Answer: the mass atomic of this element would be 268.1 u
I believe that the answer is D.
I hope this helps. :)
Answer: The mole fraction of benzene will be 0.34 and mole fraction of toluene is 0.66
Explanation:
According to Raoult's law, the vapor pressure of a component at a given temperature is equal to the mole fraction of that component multiplied by the vapor pressure of that component in the pure state.
and 
where, x = mole fraction in solution
= pressure in the pure state
According to Dalton's law, the total pressure is the sum of individual pressures.
,
,
Thus (1-x0 = (1-0.34)=0.66
Thus the mole fraction of benzene will be 0.34 and that of toluene is 0.66
