Neutralisation chemistry help

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In summary: The heat of neutralization is -55.9 kJ/mol. The energy balance is (m.Cp.del_T)in = (m.del_H) + (m.Cp.del_T)out
  • #1
pikkie
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can some one help me withe this?
i want to neutralise a 400m3 of unknown solutions in pH 2 with sodium hydroxide. homework can i calculate the volume of alkaline needed? please help me!
 
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  • #2
HINT: Knowing the pH you can determine the hydrogen ion concentration.
 
  • #3
I hate such questions. You can't calculate anything without assuming that you have a solution of strong acid. Then (and only then) Hootenanny hint will work.
 
  • #4
Thank you

Thank you! I solve it already by assuming it's a strong acid and got the answer. Thank you!
 
  • #5
Borek said:
I hate such questions. You can't calculate anything without assuming that you have a solution of strong acid. Then (and only then) Hootenanny hint will work.


Borek

Ahh, yes thank you Borek. I had forgotten about week acids (never liked them anyway :grumpy: ) As Borek said, I think one would have to assume that the acid in question is a strong acid as no dissociation constant is given.
 
  • #6
Problems Again

I solved for the heat of neutralization already, I thought, but now, I got the final temperature after reaction is 121.75 oC which I think is too big.

I start with initial pH = 2 and final the conc H+ = 10^-(pH=2) then I find the mole by multipling the conc with the tank volume (400m3), the I find the mass by multiply it with MW.

To neutralise 1 mole of H+, I need 1 mole of OH-, so I balance the mole of OH- needed with the mole of H+ I calculated justnow. The I got the mass and volume of NaOH needed to neutralize the pH 2.

The heat of neutralization is -55.9 kJ/mol. The energy balance is (m.Cp.del_T)in = (m.del_H) + (m.Cp.del_T)out

But since i use the initial temperature and reference temperature both also 25 oC, so the (m.Cp.del_T)in is cancelled. What left is only
-(m.del_H) = (m.Cp.del_T)out

The part that confused me here is what m should I use for these m.del_H and m.Cp.del_T. I obtained the answer stated ealier (121.75 oC) by using the mass for m.del_H is the mass of water produced and the mass for m.Cp.del_H is the mass of the total mass of NaOH+H2SO4 that reacted. Is this correct? If yes, is the temperature I got reasonable? If not, what's my mistake?
 

1. What is neutralisation in chemistry?

Neutralisation is a chemical reaction between an acid and a base that results in the formation of a salt and water. The acid and base neutralize each other, meaning that they cancel out each other's properties and produce a neutral solution.

2. How does neutralisation occur?

Neutralisation occurs when an acid and a base are mixed together in the correct proportions. The acid donates a proton (H+) to the base, forming water. This reaction also produces a salt, which is a compound made up of the positive ion from the base and the negative ion from the acid.

3. What is the purpose of neutralisation in chemistry?

Neutralisation is used to neutralize the acidic or basic properties of a substance. This is important in many applications, such as in the production of medicines, cleaning products, and in environmental processes to neutralize pollutants.

4. How is the strength of an acid or base determined in neutralisation reactions?

The strength of an acid or base is determined by the concentration of hydrogen ions (H+) or hydroxide ions (OH-) in a solution. The stronger the acid or base, the higher the concentration of these ions, and the more acidic or basic the solution will be.

5. What are some real-life examples of neutralisation reactions?

Some examples of neutralisation reactions include when antacid tablets are used to neutralize excess stomach acid, when baking soda is used to neutralize the acidity in a recipe, and when lime is added to acidic soil to neutralize it for plant growth. It is also commonly used in wastewater treatment and in the production of fertilizers.

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