The focal length, like you said it's the distance between the FOCAL point and the mirror.
Hope this helps.... :)
Answer:
The strength of an acid or alkali depends on the degree of dissociation of the acid or alkali in water. The degree of dissociation measures the percentage of acid molecules that ionise when dissolved in water. He could use universal indicators or litmus paper for this.
Explanation:
(See answer for the explanation)
<u>Answer:</u> Osmolarity of the sodium chloride solution is 18 Osmol/L.
<u>Explanation:</u>
Osmolarity is defined as the the concentration of the solution which is expressed as the total number of solution particles present in one liter of solvent.
We are given the molarity of the solution which is 3mol/L and to convert it into osmolarity, we will multiply the number of osmoles that are produced by the solute.
Osmole is defined as the particles that contribute to the osmotic pressure of a solution.
The solute given here is sodium chloride (NaCl). Number of osmoles can be determined by the dissociation of this solvent into ions.
The equation given by the dissociation of NaCl:

1 mole of sodium chloride produces 2 moles of ions.
So, 3 moles of sodium chloride will produce = (3 × 2) = 6 moles of ions.
Hence, osmolarity of the sodium chloride solution will be 
I believe it is C, but I can't guarantee it.
Yes because they atom with a stable octet electrons is less reactive it does not need any more electrons while an atom that has an partially filled electrons need more electrons to complete octet structure