Answer to Question #163981 in General Chemistry for muna mohamed

Question

Purpose

Determine the concentration of a base by titrating an acid of known concentration and volume.

Material

Chemicals

- HCl, NaOH, phenolphthalein

Apparatus:

- burette brush, burette, funnel, pipette, pipetter, Erlenmeyer flask, support stand, burette clamp

Safety

• Safety goggles and lab aprons should always be worn when working with chemicals.
• This lab will be performed using small quantities of chemicals (micro-scale chemistry).

Procedure

1. Wash all your equipment (and a burette), using a brush, soap and water. Rinse well with water.
2. Rinse the burette once with the acid solution.
3. Place the burette in its support and close the tap.
4. Using a funnel, fill the burette with a solution of HCl 0.1 M.
5. Open the burette’s tap, until the volume of acid reaches 0 mL.
6. Using a 10.0 mL pipette, measure exactly 10.0 mL a solution of NaOH and place it in a 125 mL Erlenmeyer.
7. Add four drops of phenolphthalein to the Erlenmeyer.
8. Place the Erlenmeyer under the burette.
9. While "swirling" the Erlenmeyer (with the base), SLOWLY add the acid from the burette, until the colour change is permanent.
10. Note the volume of acid necessary to neutralise 10.0 mL of the NaOH solution.
11. Repeat this procedure three more times.

Sample Results

Table #1: Volumes of HCl and concentrations of NaOH for the 4 Titration Trials

Titration Volume of HCl used(mL)

+ Volume of

NaOH used (mL)

#1

32.1 HCL

0.3321 NaOH

 

#2

33.5 HCL

0.335 NaOH

 

#3

32.9 HCL

0.329 NaOH

 

#4

32.3 HCL

0.323 NaOH

 

Average

 32.7 HCL

0.327

MY QUESTION IS :  Write a balanced equation for the neutralization reaction.

2. Using the avg. volume HCl needed to neutralize 10.0 mL of NaOH, calculate the concentration of the NaOH. Show all your work.

Conclusion:

Briefly state the results for the laboratory, in general. This should be no more than two sentences.

1. Why must you ensure that all your equipment is washed before doing this lab?
2. Why must you repeat the lab four times?

Answer 1

1.Write a balanced equation for the neutralization reaction.

HCl + NaOH → NaCl + H₂O

2. Using the avg. volume HCl needed to neutralize 10.0 mL of NaOH, calculate the concentration of the NaOH. Show all your work.

equation

M = moles solute / liters solution

=0.327/0.0327

=10 M

Conclusion:

Briefly state the results for the laboratory, in general. This should be no more than two sentences.

Hydrochloric acid reacts with sodium hydroxide to form sodium chloride (the salt) and water. Sodium chloride is made up of Na+ cations from the base (NaOH) and Cl- anions from the acid (HCl). HCl+NaOH→H2O+NaCl.

1.Why must you ensure that all your equipment is washed before doing this lab?

It is necessary that the glassware which we use during titration needs to be clean and dry before use because otherwise the remaining reagents will get mixed up with the solutions. As a result, this will lead to a change in analysis results.

2.Why must you repeat the lab four times?

to ensure you have an accurate result, as there is the potential for both random and systematic errors to affect your results.