Question 3 • 26-27 - C - RUSD Chemistry in the Earth System
Consider RbOH rightarrow Rb raised to the plus plus OH raised to the negative power power and these information. triangle cap h sub lat is equal to negative 765 point 0 1 kJ/mol triangle cap h sub hydr of Rb raised to the plus power is equal to negative 315 point 2 kJ/mol triangle cap h sub hydr of OH to the th power is not equal to negative 532 point 7 kJ/mol What is the triangle cap h sub sol rounded to the correct number of significant figures? Use triangle cap h sub sol is equal to negative triangle cap h sub lat plus triangle cap h sub hydr
Answer
A
negative 82 point 9 kJ/mol
B
negative 1 comma 612 point 9 kJ/mol
C
negative 82 point 8 9 kJ/mol
D
negative 1 comma 612 point 9 1 kJ/mol
Explanation
Add the hydration enthalpies: −315.2 + (−532.7) = −847.9 kJ/mol. Then use ΔH_sol = −ΔH_lat + ΔH_hydr: −(−765.01) + (−847.9) = −82.89 kJ/mol. The hydration values are given to one decimal place, so round the result to one decimal place: −82.9 kJ/mol, choice A.
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