Answer:
Option 4. There's no hydrogen bonding between HBr molecules at all.
Explanation:
<h3>SiH₄</h3>
SiH₄ molecules are tetrahedral and symmetric. Dipoles due to the polar Si-H bonds balance each other. SiH₄ molecules are nonpolar. Only instantaneous dipoles are possible between those molecules.
<h3>C₆H₆ Benzene</h3>
Similar to SiH₄, benzene is symmetric. Dipoles due to the weakly polar C-H bonds balance each other. Benzene molecules are nonpolar. Only instantaneous dipoles are possible between those molecules.
<h3>NH₃</h3>
There are two conditions for hydrogen bonding to take place:
- H atoms are directly bonded to a highly electronegative element: Nitrogen, Oxygen, or Fluorine.
- There is at least one lone pair of electrons nearby.
Consider the Lewis structure of NH₃. There are three H atoms in each NH₃ molecule. Each of the three H atoms is bonded directly to the N atom with a highly polar N-H bond. Also, there is a lone pair of electrons on the N atom. Hydrogen bonding will take place between NH₃ molecules.
NH₃ is a relatively small molecule. As a result, hydrogen bonding will be the dominant type of intermolecular force between NH₃ molecules.
<h3>HBr</h3>
There are three lone pairs on the Br atom in each HBr molecule. However, no H atom is connected to any one of the three highly electronegative elements: N, O, or F. The Br atom isn't electronegative enough for the H atom to form hydrogen bonding. HBr molecules are polar. As a result, the dominant type of intermolecular forces between HBr molecules will be dipole-dipole interactions (A.k.a. permanent dipole.)
<h3>CaO</h3>
Calcium is a group 2 metal. Oxygen is one of the three most electronegative nonmetal. (Again, the most electronegative elements are: Nitrogen, Oxygen, and Fluorine.) As a main group metal, Ca atoms tend to lose electrons and form positive ions. Oxygen will gain those electrons to form a negative ion. As a result, CaO will be an ionic compound full of Ca²⁺ and O²⁻ ions. Forces between ions with opposite charges are called ionic bonds.
<h2>Energy is conserved. It never appears or disappears. It just changes from one kind of type to another. The Universe contains the same amount of energy it started with. This amount can never change.</h2><h2>
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In buffer solution there is an equilibrium between the acid HA and its conjugate base A⁻: HA(aq) ⇌ H⁺(aq) + A⁻(aq).
When acid (H⁺ ions) is added to the buffer solution, the equilibrium is shifted to the left, because conjugate base (A⁻) reacts with hydrogen cations from added acid, according to Le Chatelier's principle: H⁺(aq) + A⁻(aq) ⇄ HA(aq). So, the conjugate base (A⁻) consumes some hydrogen cations and pH is not decreasing (less H⁺ ions, higher pH of solution).
A buffer can be defined as a substance that prevents the pH of a solution from changing by either releasing or absorbing H⁺ in a solution.
Buffer is a solution that can resist pH change upon the addition of an acidic or basic components and it is able to neutralize small amounts of added acid or base, pH of the solution is relatively stable
