Answer: the following are essential factors to be considered when choosing a solvent for crystallization
1. The crystallization solvent should not dissolve the substance to be purified at room temperature, but it should dissolve it well at the solvent’s boiling point
2. The solvent should dissolve soluble impurities well at room temperature.
3. The solvent should not dissolve insoluble impurities even at the solvent’s boiling
point.
4. The solvent must not react with the substance to be purified .
Answer 2.04
Explanation
Electronegativity decreases down the group and increases across the period in the periodic table.
In the period two of the periodic table,we have the following values for electronegativities with respect to its elements.
Li...........0.98
Be.........1.57
B..........2.04
C.........2.55
N..........3.04
O...........3.44
F...........3.98
Ne........n.a
The value that should be where M is is 2.04
The half-life of Th-232 is 1.405 × 10¹⁰ years
Time elapsed = 2.8 x 10⁹ years
Equation of radioactive decay:
A = A₀ = (1/2)^ t/t₁/₂
Thus, the percentage of thorium-232 in the rock that was dated at 2.8 billions year = 87.1%
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