Answer:- 0.138 M
Solution:- The buffer pH is calculated using Handerson equation:

acts as a weak acid and
as a base which is pretty conjugate base of the weak acid we have.
The acid hase two protons(hydrogen) where as the base has only one proton. So, we could write the equation as:

Phosphoric acid gives protons in three steps. So, the above equation is the second step as the acid has only two protons and the base has one proton.
So, we will use the second pKa value. The acid concentration is given as 0.10 M and we are asked to calculate the concentration of the base to make a buffer of exactly pH 7.00.
Let's plug in the values in the equation:



Taking antilog:


On cross multiply:
[base] = 1.38(0.10)
[base] = 0.138
So, the concentration of the base that is
required to make the buffer is 0.138M.
Answer:
4.88 x 10²⁴atoms
Explanation:
Given parameters:
Number of moles of oxygen = 8.1moles
Problem:
To find the number of atoms in 8.1moles of oxygen.
Method in solving the problem:
We know that a mole of a substance contains Avogadro’s number of particles which is 6.02 x 10²³
The particles can be molecules, atoms, etc.
Solution:
From the concept of mole,
Number of atoms =
number of moles x 6.02 x 10²³
Number of atoms = 8.1 x 6.02 x 10²³
Number of
atoms of oxygen = 48.8 x 10²³ atoms
= 4.88 x 10²⁴atoms
Answer:
hydroxide and hydrogen
Explanation:
When a metal reacts with water, a metal hydroxide and hydrogen are formed. Sodium reacts vigorously with water.
If two atoms** have the same number of protons, they are the same element. They have the same atomic number. The only thing that would change with the number of neutrons is the mass number.