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Home Q & A Board Science-Related Homework Help Chemistry (Moderator: Laser_3)
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mikael mikael
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13 years ago
What is the lattice energy of KI ( Hsoln =+21.5 kJ/mol) and MgCl2 ( Hsoln = –150 kJ/mol)? Use Table 13.1 to determine heat of hydration.
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#1
13 years ago
The heat of hydration for KI is

–336 kJ/mol (K+) + –247 kJ/mol (I–) = –583kJ/mol.

The heat of hydration for MgCl2 is

–1903 kJ/mol (Mg2+) + 2(–313 kJ/mol) (Cl–) = –2529kJ/mol

Hsoln = –U +  Hhydration

For KI

Hsoln = –U +  Hhydration

+21.5 kJ/mol = –U + –583 kJ/mol
604.5 kJ/mol = –U
604 kJ/mol = U = lattice energy

Since this was addition and subtraction, the fewest decimal places were used to determine significant figures. For MgCl2

Hsoln = –U +  Hhydration

–150 kJ/mol = –U + –2529 kJ/mol
2379 kJ/mol = –U
–2379 kJ/mol = U
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