Astudentlearnsthationiccompoundshavesignificantcovalentcharacterwhenacationhasap

Question

Astudentlearnsthationiccompoundshavesignificantcovalentcharacterwhenacationhasapolarizingeffect on a large anion. As a result, the student hypothesizes that salts composed of small cations and large anions should have relatively low melting points. (a) Select two compounds from the table and explain how the data support the student’s hypothesis. (b) Identify a compound from the table that can be dissolved in water to produce a basic solution. Write the net ionic equation for the reaction that occurs to cause the solution to be basic. LiI 449 oC KI 686 oC LiF 845 NaF 993

Explanation / Answer

a) LiI and KI have small melting points formef from

The ionic radius of the Li + cation is smaller than the ionic radius of the Na + cation.

The ionic radius of the K+ cation is larger than the i onic radius of the I- ions.

They have low melting points. 449 and 686. Hence, the student claim is justified.

NaF is formed from strong base (NaOH) and HF( weak acid)

Na+ +OH- + H+ F-   ----> Na++F- +H2O(l)

net ionic equation H+ (aq) + OH- (aq) ---> H2O(l)

LIF is fromed from LiOH ( strong base) and HF ( weak acid)

H+(aq)+ OH- (aq)---> H2O(l)

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