Question

put the following compounds in order of decreasing melting point. li3p, mgbr2, libr, ca3n2 1 choose 2 choose 3 choose 4 choose

Explanation:

Step1: Recall ionic - bond strength factor

Ionic compounds' melting points depend on the strength of ionic bonds. Stronger ionic bonds lead to higher melting points. The strength of an ionic bond is related to the product of ionic charges (Coulomb's law) and the ionic radii.

Step2: Analyze charges and ionic radii of ions in compounds

• In $Ca_3N_2$, $Ca^{2 + }$ and $N^{3 - }$ have charges of + 2 and - 3 respectively. The large product of charges ($2\times3 = 6$) and relatively small ionic radii contribute to strong ionic bonds.
• In $MgBr_2$, $Mg^{2+}$ has a charge of + 2 and $Br^-$ has a charge of - 1. The product of charges is $2\times1=2$.
• In $Li_3P$, $Li^+$ has a charge of + 1 and $P^{3 - }$ has a charge of - 3. The product of charges is $1\times3 = 3$.
• In $LiBr$, $Li^+$ has a charge of + 1 and $Br^-$ has a charge of - 1. The product of charges is $1\times1 = 1$.

Step3: Order the compounds

Based on the above - mentioned analysis of ionic - bond strength, the order of decreasing melting points is determined by the strength of ionic bonds in the compounds.

Answer:

1. $Ca_3N_2$
2. $Li_3P$
3. $MgBr_2$
4. $LiBr$