Name: Christian Harmon
Class: 10E.
Lab# 5.
Date: 2/05/2025.
Aim: To determine the mass of NaOH required to prepare 250cm3 of a 1.0 mol mol/dm3 NaOH
solution.
Apparatus:
- 25cm3 pipette
- 4 – 250mL conical flasks
- 50cm3 burette
- Clamp stand
Materials:
- Funnel
- White sheet of paper
- Phenolphthalein indicator
- 1.0 moldm-3 Sodium Hydroxide
Method:
1. The burette was rinsed with some sodium hydroxide, and using a funnel, the burette was filled
with the base.
2. A 25 cm³ sample of sulphuric acid solution was measured using a pipette and transferred into
the conical flask.
3. Two to three drops of phenolphthalein indicator were added to the conical flask, and the
contents were swirled to mix.
4. The initial burette reading (bottom of the meniscus) was taken.
5. Sodium hydroxide was slowly added to the conical flask while swirling constantly, until the
solution just turned from colorless to pink.
6. A final burette reading was taken, and the volume of base added was determined. This was
recorded as the rough titration.
7. The contents in the conical flask were discarded, and the flask was thoroughly rinsed with
distilled water.
8. The titration was repeated a few times to obtain accurate volumes.
9. The data was recorded in the table provided.
Data analysis
1. Write a balanced chemical and ionic equation for the reaction. Include state
symbols.
Balanced chemical equation:
H2SO4(aq) + 2NaOH(aq) NaSO4(aq) + 2H2O(l)
Net ionic equation:
H+(aq) + OH-(aq) H2O(l)
2. What volume of acid is required to neutralize 25cm3 of sodium hydroxide?
V = (0.1 mol/dm x 0.025 dm ) / 0.1 mol/dm = 0.025 dm = 25.00 cm
acid
3 3 3 3 3
3. Calculate how many moles of sodium hydroxide were pipetted into the conical flask.
Moles of NaOH = Concentration of NaOH x Volume of NaOH
= 1.0 mol/dm3 x 0.025 dm3 = 0.025 mol
4. Calculate how many moles of sulfuric acid reacted with sodium hydroxide in the
flask during titration.
2 moles of NaOH react with 1 mole of H₂SO₄, hence the moles of H₂SO₄ that reacted with
NaOH are:
Moles of H₂SO₄ = 0.025 mol / 2
= 0.0125 mol
5. Calculate the concentration in moldm-3 of sulfuric acid
Concentration of H₂SO₄ = 0.0125 mol / 0.025 dm3 = 0.5 mol/dm3
6. Calculate the concentration in gdm-3 of sulfuric acid
Mass concentration of H₂SO₄ = (98.079 g/mol) x (0.025 dm )3
= 49 g/dm 3
Sources of error Limitations Precautions
Because The accuracy of the titration Ensure lab coat and a pair of
phenolphthalein changes color may be impacted by minor gloves are worn
slightly, the endpoint selection variations in the volume of
might have been arbitrary, sodium hydroxide employed
which could have resulted in due to subtle variations in how
over-titration. the indicator's color shift is
interpreted.
Only
2-3 drops of phenolphthalein
Should be added to each
conical flask
Conclusion:
Based on the results obtained from this experiment, the concentration of the sulfuric acid
solution to be 98gdm-3
