Question

1. Given an atom with the Mass number of 40 and 22 neutrons, how many protons there are in the nucleus of this atom? How about electrons? How many electrons on the last shell? How many electrons, if any, does it need to comply with the octet rule?

2. What is the pH of a pure WATER solution if the concentration of H+ in water is 10-7 ?
3. Let’s assume you add acid to a solution containing a buffer. What is the buffer going to do (release or bind protons)? Hint: think about the definition of an acid & a buffer.

Answer 1

An atom with a mass number of 40 and 22 neutrons has 18 protons and electrons each, with its last shell filled complying with the octet rule. Pure water has a neutral pH of 7.0. A buffer in a solution will typically release protons when acid is added to maintain pH stability.

Step-by-step explanation:

Given an atom with a mass number of 40 and 22 neutrons, you can find the number of protons by subtracting the number of neutrons from the mass number (40 - 22 = 18 protons). Since the atom is neutral, it will have the same number of electrons as protons, which is 18 electrons. The distribution of electrons among the shells for an atom with 18 electrons will see the last shell having 8 electrons, as the first two shells can hold up to 2 and 8 electrons, respectively. The atom will not need to gain or lose electrons to comply with the octet rule, as its last shell already has 8 electrons.

The pH of a pure water solution with a hydrogen ion concentration of 10-7 is 7.0, which is considered neutral on the pH scale. This is calculated using the negative logarithm of the hydrogen ion concentration.

When adding acid to a solution containing a buffer, the buffer will generally release protons in order to maintain a stable pH level in the solution. Buffers are substances that minimize changes in the concentrations of H+ and OH- in a solution, which helps stabilize the pH.