Question

Which oxide has the highest melting point?
(A) Silicon dioxide
(B) Carbon dioxide
(C) Sulphur dioxide
(D) Carbon monoxide

Answer 1

We all know that intermolecular forces are much weaker than the covalent bonds which are strong and therefore very less amount of energy is required to break down the compounds and covalent bonds are formed when electrons are shared between atoms resulting in lower melting point and electrical conductivity.

Complete step by step solution:
We know that intermolecular forces are much weaker than the covalent bonds which are strong and therefore very less amount of energy is required to break down the compounds and covalent bonds are formed when electrons are shared between atoms resulting in lower melting point and electrical conductivity. We also know that ionic compounds form strong interactions between ions resulting in higher melting point and electrical conductivity and covalent bonds are formed when electrons are shared between atoms resulting in lower melting point and electrical conductivity.
Silicon dioxide have a very less electronegativity as we move across a period and hence it is unable to form an ionic compound instead it forms a covalent solid compound which has a very strong silicon-oxygen covalent bonds that needs to be broken so it requires a temperature of about ${2230^ \circ }C$ to melt.
Carbon monoxide contains covalent bonds as their atoms share the electrons so that their valence shell is filled but weak intermolecular forces join their molecules together which can be easily broken and thus they have a low melting point.
Carbon dioxide also has a low melting point as it is a simple molecular gas consisting of carbon and oxygen atoms that are covalently bonded together but they are held together by weak intermolecular forces.
Sulphur dioxide as we know has the weakest intermolecular forces the van der waal forces and it does not have a hydrogen which is responsible for strong intermolecular bonds hence it has a low melting point than silicon dioxide but higher than carbon dioxide.

Hence, from the above explanation we can say that our correct answer is (A).

Note: Silicon dioxide is commonly found as quartz and in a study it was found that higher levels of silica in water decreases the risk of long term memory loss or ability to think. We take into account the bond strength between the atoms when we want to find out the melting point of any substance or compound.