Put the following in order in terms of increasing melting point: SiH4, SiO2, CH4, NH3, PH3.
Lowest → Highest
(A) NH3, PH3, CH4, SiH4, SiO2
(B) SiO2, PH3, NH3, CH4, SiH4
(C) SiH4, CH4, NH3, PH3, SiO2
(D) CH4, SiH4, PH3, NH3, SiO2
(E) CH4, SiH4, SiO2, NH3, PH3
We would be interested in your thoughts and why you have them arranged in that order.
The balanced equation P4(s)+ 6H2(g) + 4PH3(g) tells us that 7.0 mol H2 reacts or produces
The correct answer is (C) SiH4, CH4, NH3, PH3, SiO2.
To determine the order of increasing melting point, we need to consider the types of bonds present in each compound. Melting point generally increases with increasing bond strength.
Silicon tetrahydride (SiH4) is a covalent compound with weak van der Waals forces between the molecules. It has the lowest melting point among the given compounds.
Methane (CH4) is also a covalent compound, but it has stronger van der Waals forces due to the larger size of carbon compared to silicon. Therefore, CH4 has a higher melting point than SiH4.
Ammonia (NH3) is a polar covalent compound with hydrogen bonding between molecules. Hydrogen bonding is stronger than van der Waals forces, resulting in a higher melting point for NH3 compared to CH4.
Phosphine (PH3) is similar to ammonia as it is also a polar covalent compound with hydrogen bonding. Thus, PH3 has a higher melting point than NH3.
Silicon dioxide (SiO2) is a giant covalent compound with a network of strong covalent bonds between silicon and oxygen. This makes it have the highest melting point among the given compounds.
Therefore, the correct order of increasing melting point is SiH4, CH4, NH3, PH3, SiO2, which corresponds to option (C).
To determine the order of increasing melting point, we need to consider the intermolecular forces present in each compound. The strength of intermolecular forces directly affects the melting point because stronger forces require more energy to break and transition from solid to liquid.
1. SiH4 (Silane): Silane is a nonpolar molecule with only weak London dispersion forces, which are the weakest intermolecular forces. Therefore, it has the lowest melting point.
2. CH4 (Methane): Methane is also a nonpolar molecule with weak London dispersion forces. However, since carbon is more electronegative than silicon, methane has slightly stronger intermolecular forces than silane, leading to a higher melting point.
3. NH3 (Ammonia): Ammonia is a polar molecule with dipole-dipole interactions. These interactions are stronger than London dispersion forces. Therefore, ammonia has a higher melting point than silane and methane.
4. PH3 (Phosphine): Phosphine is a polar molecule similar to ammonia. It also has dipole-dipole interactions and a higher melting point than ammonia.
5. SiO2 (Silicon Dioxide): Silicon dioxide is a giant covalent structure with a high melting point. It forms a network of strong covalent bonds, which require a significant amount of energy to break. Therefore, silicon dioxide has the highest melting point among the given compounds.
Based on this analysis, the correct order in terms of increasing melting point is:
(C) SiH4, CH4, NH3, PH3, SiO2.