Consider diamond and graphite. Which of the following is true?
(A) Graphite should have a higher melting point than diamond.
(B) Differences in composition account for the different properties of gaphite and diamond.
(C) Amorphous soilds are likely to have highe meltong points than their crystalline counterparts.
(D) Introducing an impurity into a crystalline material should increase the observed melting point.
(E) The carbon atoms in diamond are sp32 hybridized.
E is correct. As we have four bondings, and no one is in any way to be preferred, it is logical that they are sp³ hybridized.
I don't see any correct answers listed although E comes the closest. If you had sp3 instead of sp32 I would go with E being correct.
To determine which of the statements is true, let's analyze each one:
(A) Graphite should have a higher melting point than diamond:
To determine this, we need to consider the bonding in diamond and graphite. Diamond consists of a three-dimensional network of carbon atoms bonded together by strong covalent bonds. On the other hand, graphite has a layered structure with weaker interlayer forces. Due to these differences in bonding, diamond has a higher melting point compared to graphite. Therefore, this statement is false.
(B) Differences in composition account for the different properties of graphite and diamond:
This statement is true. The properties of diamond and graphite are primarily due to the differences in their structures and bonding. Diamond is a pure form of carbon with a tetrahedral arrangement of carbon atoms, while graphite has a layered structure where carbon atoms are arranged in hexagonal rings. These structural differences result in different physical properties such as hardness, electrical conductivity, and melting point.
(C) Amorphous solids are likely to have higher melting points than their crystalline counterparts:
This statement is false. Amorphous solids do not possess a regular or ordered arrangement of atoms like crystalline solids do. Consequently, amorphous solids have weaker intermolecular forces, which generally result in lower melting points compared to their crystalline counterparts. Therefore, this statement is incorrect.
(D) Introducing an impurity into a crystalline material should increase the observed melting point:
This statement is ambiguous. The effect of introducing an impurity into a crystalline material on the observed melting point depends on various factors such as the type of impurity and its interaction with the crystal lattice. In some cases, impurities can disrupt the crystal lattice, weakening the intermolecular forces and possibly lowering the melting point. However, in other instances, impurities can strengthen the crystal lattice, increasing the melting point. Therefore, this statement is not universally true.
(E) The carbon atoms in diamond are sp3 hybridized:
This statement is true. In diamond, each carbon atom is covalently bonded to four neighboring carbon atoms in a tetrahedral arrangement. The bonding in diamond involves the hybridization of the carbon orbitals, resulting in sp3 hybridized carbon atoms. This hybridization allows each carbon atom in diamond to form sigma bonds with its four neighboring atoms, creating a rigid network structure. Therefore, this statement is correct.