<u>Answer:</u> The molarity of citric acid that is commercially available lemon juice is 0.416 M
<u>Explanation:</u>
To calculate the concentration of acid, we use the equation given by neutralization reaction:

where,
are the n-factor, molarity and volume of acid which is 
are the n-factor, molarity and volume of base which is NaOH.
We are given:

Putting values in above equation, we get:

Hence, the molarity of citric acid that is commercially available lemon juice is 0.416 M
Answer: solid
Explanation: Chemical reactions are those which involve rearrangement of atoms.
Chemical changes are accompanied by following changes:
1) Absorption or release of heat
2) Change in color
3) Formation of gas bubbles
4) Formation of a solid product called as precipitate
Example of formation of precipitate or solid in chemical reaction:
It's A. volume
Pressure =

with const depends on the chosen unit of volume
I think so...