A chemist has 2.0 mol of methanol (CH₃OH). The molar mass of methanol is 32.0 g/mol. What is the mass, in grams, of the sample?
2 answers:
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Answer : The molal freezing point depression constant of liquid X is,
Explanation : Given,
Mass of urea (solute) = 5.90 g
Mass of liquid X (solvent) = 450 g = 0.450 kg
Molar mass of urea = 60 g/mole
Formula used :
where,
= change in freezing point
= freezing point of solution =
= freezing point of liquid X =
i = Van't Hoff factor = 1 (for non-electrolyte)
= Molal-freezing-point-depression constant = ?
m = molality
Now put all the given values in this formula, we get
Therefore, the molal freezing point depression constant of liquid X is,
Answer: 10.2 grams
Explanation:
The balanced chemical reaction is :
According to the ideal gas equation:
P = Pressure of the gas = 740 torr = 0.97 atm (760torr=1atm)
V= Volume of the gas = 12.0 L
T= Temperature of the gas = 19°C = 292 K
R= Gas constant = 0.0821 atmL/K mol
n= moles of gas
According to stoichiometry:
2 moles of hydrogen are generated by = 1 mole of
Thus 0.48 moles of hydrogen are generated by = moles of
Mass of
Thus 10.2 grams of are needed to generate 12.0 L of hydrogen gas if the pressure of hydrogen is 740. torr at 19°C