Answer:
m = 3 moles/kg
Explanation:
This is a problem of freezing point depression, and the formula or expression to use is the following:
ΔT = i*Kf¨*m (1)
Where:
ΔT: Change of temperature of the solution
i: Van't Hoff factor
m: molality of solution
Kf: molal freezing point depression of water (Kf = 1.86 °C kg/mol)
Now, the value of i is the number of moles of particles obtained when 1 mol of a solute dissolves. In this case, we do not know what kind of solution is, so, we can assume this is a non electrolyte solute, and the value of i = 1.
Let's calculate the value m, which is the molality solving for (1):
m = ΔT/Kf (2)
Finally, let's calculate ΔT:
ΔT = T2 - T1
ΔT = 0 - (-5.58)
ΔT = 5.58 °C
Now, let's replace in (2):
m = 5.58/1.86
<em>m = 3 moles/kg</em>
<em>This is the molality of solution.</em>
<em>The other data of mass, can be used to calculate the molecular mass of this unknown solid, but it's not asked in the question.</em>
The second one and the 2 last ones
Answer:
Explanation:
x in (-oo:+oo)
2 < (1/2)*x-3 // - (1/2)*x-3
2-((1/2)*x)+3 < 0
(-1/2)*x+2+3 < 0
5-1/2*x < 0 // - 5
-1/2*x < -5 // : -1/2
x > -5/(-1/2)
x > 10
x in (10:+oo)
(10:+oo)
Answer:
B) The amount of vitamin D gained in 1 day.
Explanation:
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