Acid-Base Titrations - Soda Lime and Hydrochloric Acid

  • Thread starter ajassat
  • Start date
  • Tags
    Acid
In summary, to completely neutralize 2.50g of a mixture of 85.0% NaOH and 15.0% CaO, approximately 133 cm3 of 0.500M Hydrochloric Acid is required. This is calculated by considering the reactions separately and finding the number of moles of each substance, then using the volume formula (V=n/c) to find the required volume of acid. The main challenge is determining the relative formula mass of the mixture and writing a balanced equation for the titration.
  • #1
ajassat
55
0

Homework Statement


"Soda lime is 85.0% NaOH and 15.0% CaO. What volume of 0.500M Hydrochloric Acid is required to completely neutralise 2.50g of the Soda Lime?"
Hint: Consider the reactions separately


Homework Equations



Formation of Soda Lime:
CO2 + H2O >> H2CO3
H2CO3 + 2NaOH >> Na2CO3 + heat
Na2CO3 + Ca(OH)2 >> CaCO3 + 2NaOH

number of moles = mass / relative formula mass
volume = number of moles divided by concentration


The Attempt at a Solution



1)Find the number of moles of Soda Lime (from the equations describing its formation)
2)Deduce the number of moles of HCL from the equation describing the titration
3)Work out volume of HCL using number of moles/0.500

4. Main problems encountered

*I don't know the chemical formula for soda lime/I cannot deduce its relative formula mass
*Because of the above I cannot write a balanced equation for the titration

Guidance is greatly appreciated.

Regards,
Adam
 
Physics news on Phys.org
  • #2
ajassat said:
Hint: Consider the reactions separately

Forget about soda lime and its production, it doesn't matter. You have 2.5 g of a mixture of NaOH and CaO. How much NaOH in the mixture? How much acid required for titration of NaOH? What about CaO?
 
Last edited by a moderator:
  • #3
Borek said:
Forget about soda lime and its production, it doesn't matter. You have 2.5 g of a mixture of NaOH and CaO. How much NaOH in the mixture? How much acid required for titration of NaOH? What about CaO?

--
chemical calculators - buffer calculator, concentration calculator
www.titrations.info - all about titration methods

Since there 85% of NaOH, the mass of NaOH in the 2.5g mixture is:
(85/100)*2.5 = 2.12500

Therefore the mass of CaO in the mixture is:
2.5 - 2.12500 = 0.375g

The titration of NaOH:
NaOH + HCL >> NaCl + H20
number of moles of NaOH = m/Mr = 2.12500/40 = 0.053125 mol
From equation number of moles of HCL = 0.053125 mol
Therefore volume(HCL) = n/c = (0.053125/0.500)*1000 = 106.25 cm3

Is this first value for volume correct?
 
  • #4
Looks OK.
 
Last edited by a moderator:
  • #5
Continuing with the titration of CaO

CaO + 2HCL >> CaCl2 + H2O

number of moles = m/mr = 0.375/56 = 0.00669642857
From equation, number of moles (HCL) = 2*0.00669642857 = 0.013938571
Therefore:
V = n/c = (0.0134/0.500)*1000 = 26.8cm3
 
Last edited:
  • #6
Adding the two calculated volumes gives
total volume of HCL required = 26.8 + 106.25 = 133.05cm3 or 133cm3 (to 3 sig fig0

Borek: Please confirm :)
 
Last edited:
  • #7
Approach is correct, but you have eaten one digit, so the final result is off.
 
Last edited by a moderator:
  • #8
It should be: 0.0133928571
Which when rounded to 3 sig fig is 0.0134

NB: See adjusted Calculation and answer
 
Last edited by a moderator:

1. What is an acid-base titration?

An acid-base titration is a laboratory technique used to determine the concentration of an acid or base solution by reacting it with a known concentration of another acid or base solution. The reaction between the two solutions is monitored using an indicator or pH meter, and the point of neutralization is used to calculate the concentration of the unknown solution.

2. What is soda lime and how is it used in acid-base titrations?

Soda lime is a mixture of calcium hydroxide and sodium hydroxide that is used as an absorbent in carbon dioxide scrubbers. In acid-base titrations, soda lime is used to remove carbon dioxide from the air in the titration flask, allowing for accurate measurements and preventing the formation of carbonic acid, which can affect the results of the titration.

3. Why is hydrochloric acid commonly used in acid-base titrations?

Hydrochloric acid (HCl) is a strong acid that is commonly used in acid-base titrations because it reacts completely with a strong base, making it easy to determine the endpoint of the titration. Additionally, HCl is readily available and relatively inexpensive, making it a practical choice for laboratory use.

4. How is the endpoint of an acid-base titration determined?

The endpoint of an acid-base titration is determined using an indicator or a pH meter. An indicator is a substance that changes color at a specific pH, indicating the point of neutralization. A pH meter measures the pH of the solution and detects the sharp change in pH that occurs at the endpoint of the titration.

5. What are some sources of error in acid-base titrations?

Some common sources of error in acid-base titrations include incorrect measurement of solutions, contamination of solutions, and improper calibration of equipment. In addition, human error, such as misreading the volume on a burette or not waiting for the color change of the indicator, can also lead to inaccurate results.

Similar threads

  • Biology and Chemistry Homework Help
Replies
2
Views
2K
  • Biology and Chemistry Homework Help
Replies
4
Views
3K
  • Biology and Chemistry Homework Help
Replies
2
Views
21K
  • Biology and Chemistry Homework Help
Replies
7
Views
4K
  • Biology and Chemistry Homework Help
Replies
3
Views
4K
  • Biology and Chemistry Homework Help
Replies
1
Views
1K
  • Biology and Chemistry Homework Help
Replies
1
Views
11K
  • Biology and Chemistry Homework Help
Replies
10
Views
2K
  • Biology and Chemistry Homework Help
Replies
6
Views
6K
  • Biology and Chemistry Homework Help
Replies
2
Views
4K
Back
Top