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Answer:
i) 16 mL of ethanol
ii) maximum amount recoverable = 15.52 g; percentage recovery = 97%
iii) maximum amount recoverable = 15.1 g
percentage recovery = 94.4%
Explanation:
Solubility = mass/volume
i) mass of ethanol recovered per mL of ethanol when cooled from 78 °C to 0 °C = 0.13 - 0.03 = 0.10 g
Therefore 1.60 g of Y will require a minimum of 1.60 x 1 mL/0.10 g = 16 mL of ethanol
ii) maximum amount of Y that can be recovered is given as :
mass of Y left in solution after recrystallization, x is obtained
0.03 g/mL = x g/16 mL
x = 0.48 g
maximum amount recoverable = 16 - 0.48 = 15.52 g
percentage recovery = (15.52/16) x 100 % = 97%
iii) if 30 mL of ethanol were used:
mass of Y left in solution after recrystallization, x is obtained;
0.03 g/mL = x g/30 mL
x = 0.03 x 30 = 0.9 g
maximum amount recoverable = 16 - 0.9 = 15.1 g
percentage recovery = (15.1/16) x 100% = 94.4%
Answer: element.
Justification:
1) A molecule is the union of two or more atoms.
2) When two or more atoms of different elements bond together, the molecule formed is a compound.
For example: one atoms of hydrogen and one atom of chlorine form the molecule HCl, which is a compound (hydrogen chloride).
3) When the molecules is formed by two atoms of the same element, it is not called a compound, but element. Some examples of this are the diatomic gases:
H₂: hydrogen
Cl₂: chlorine
Br₂: bromine
O₂: oxygen
S₂: sulfur
N₂: nitrogen.
Answer:
7.5 kcal
Explanation:
1.0 cal /g-C * 100 g * (100- 25 C) = 7500 cal = 7.5 kcal
4. Isotopes of the same element
