To prepare and standrize 100 ml of 0.1 naoh solution using oxalic acid as primary standard........
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Preparation and Standardization of 0.1 M NaOH (100 mL) Using Oxalic Acid
Part 1 - Preparation of 0.1 M NaOH (100 mL)
What You Need
- NaOH pellets
- Distilled water
- 100 mL volumetric flask
- Weighing balance
- Beaker and glass rod
How Much NaOH to Weigh?
Formula: Mass = Molarity × Volume (L) × Molar mass
- Molar mass of NaOH = 40 g/mol
- Mass = 0.1 × 0.1 × 40 = 0.4 g
Steps
- Weigh 0.4 g of NaOH pellets on a watch glass (quickly - NaOH absorbs moisture from air).
- Dissolve the pellets in a small amount of distilled water in a beaker. Stir well.
- Allow the solution to cool to room temperature (dissolving NaOH generates heat).
- Transfer the solution carefully into a 100 mL volumetric flask.
- Rinse the beaker 2-3 times with distilled water and add the washings to the flask.
- Add distilled water up to the 100 mL mark (bottom of the meniscus).
- Stopper and mix well by inverting the flask several times.
Note: This is an approximate (rough) solution. Its exact concentration is determined by standardization.
Part 2 - Standardization of NaOH Using Oxalic Acid
Why Oxalic Acid?
Oxalic acid dihydrate (H₂C₂O₄ · 2H₂O) is a primary standard because it is:
- Pure and stable
- Has a known molecular weight (126.07 g/mol)
- Easy to weigh accurately
The Chemical Reaction
$$\text{H}_2\text{C}_2\text{O}_4 + 2\text{NaOH} \rightarrow \text{Na}_2\text{C}_2\text{O}_4 + 2\text{H}_2\text{O}$$
- 1 mole of oxalic acid reacts with 2 moles of NaOH
- So: n-factor of oxalic acid = 2 (diprotic acid)
How Much Oxalic Acid to Weigh?
To make 100 mL of 0.05 M oxalic acid (equivalent to 0.1 N, which matches 0.1 N NaOH):
Mass = 0.05 × 0.1 × 126.07 = 0.63 g
Weigh approximately 0.63 g of oxalic acid dihydrate.
Equipment Needed
| Item | Purpose |
|---|---|
| Burette (50 mL) | To hold NaOH solution |
| Pipette (10 mL) | To measure oxalic acid |
| Conical flask (250 mL) | Titration vessel |
| Phenolphthalein indicator | To detect endpoint |
| White tile | To see color change clearly |
Steps for Standardization (Titration)
Setting up:
- Rinse the burette with distilled water, then rinse with a little NaOH solution. Fill the burette with NaOH solution. Note the initial burette reading.
- Rinse the pipette with oxalic acid solution. Pipette out exactly 10 mL of the standard oxalic acid solution into a conical flask.
Titrating:
- Add 2-3 drops of phenolphthalein indicator to the flask. Solution remains colorless.
- Run NaOH from the burette slowly into the oxalic acid, swirling constantly.
- As you approach the endpoint, add NaOH drop by drop.
- The endpoint is reached when a faint permanent pink color appears and does not disappear for at least 30 seconds.
- Note the final burette reading.
Repeat: Do the titration at least 3 times to get concordant readings (readings within 0.1 mL of each other).
Part 3 - Calculation
Volume of NaOH used = Final reading - Initial reading = V mL (average of concordant readings)
Using the formula:
$$M_1 V_1 = M_2 V_2 \times \text{(ratio from equation)}$$
Or equivalently (normality formula):
$$N_1 V_1 = N_2 V_2$$
Where:
- N₁ = Normality of oxalic acid = 0.1 N
- V₁ = Volume of oxalic acid = 10 mL
- N₂ = Normality of NaOH = ?
- V₂ = Volume of NaOH used from burette
$$N_{\text{NaOH}} = \frac{N_1 \times V_1}{V_2} = \frac{0.1 \times 10}{V_2}$$
Example: If you used 9.8 mL of NaOH:
$$N_{\text{NaOH}} = \frac{0.1 \times 10}{9.8} = 0.102 \text{ N}$$
Quick Summary Table
| Step | Action |
|---|---|
| 1 | Weigh 0.4 g NaOH, dissolve, make up to 100 mL |
| 2 | Weigh 0.63 g oxalic acid, dissolve, make up to 100 mL |
| 3 | Pipette 10 mL oxalic acid into flask |
| 4 | Add 2 drops phenolphthalein |
| 5 | Titrate with NaOH from burette |
| 6 | Endpoint = faint permanent pink |
| 7 | Calculate: N(NaOH) = (0.1 × 10) / V(NaOH used) |
Key Points to Remember
- NaOH is hygroscopic - weigh fast and store in a closed bottle
- Always use fresh distilled water (CO₂-free preferred)
- Phenolphthalein turns pink in base - endpoint is the first permanent pink
- Repeat titration 3 times and use the average volume
- The standardized NaOH concentration may differ slightly from 0.1 M - that is normal and expected
Create a printable quick reference card for this procedure
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NaOH Quick Reference Card
PDF Document · PDF
The A4 card is laid out in 5 clean sections - everything fits on one page:
| Section | What's inside |
|---|---|
| Header banner | Title, concentration, primary standard at a glance |
| Chemicals & Apparatus | Exact weights/volumes + all glassware needed |
| Chemical Reaction | Balanced equation, molar masses, n-factor, indicator |
| Part A - Preparation | 6 numbered steps with titles and details |
| Part B - Standardization | 6 numbered titration steps |
| Calculation formula | N₁V₁ = N₂V₂ with worked example + key reminders |
Print at 100% on A4 paper (no scaling). Color printing gives the best result but it reads fine in black-and-white too.
To estimation of barium sulfate...... procedure flash card chemical with h2so4 and bacl2
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Your BaSO₄ estimation flashcard is ready!
BaSO4 Estimation Flashcard
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Here is everything packed into one A4 page:
| Section | Content |
|---|---|
| Principle | How Ba²⁺ precipitates as BaSO₄ - 5 bullet points |
| Chemicals & Apparatus | BaCl₂, H₂SO₄, filter paper, crucible, furnace |
| Balanced Equation | BaCl₂ + H₂SO₄ → BaSO₄↓ + 2HCl with molar masses |
| 6 Procedure Steps | Dissolve → Acidify → Precipitate → Filter → Ignite → Weigh |
| Calculations | Wt BaSO₄ = W₂ - W₁, % Ba formula, gravimetric factor 0.5885 |
| Observations & Key Points | 8 tips with green/red/blue color coding |
| Sources of Error | 5 common mistakes to avoid (co-precipitation, incomplete washing, etc.) |
Print at 100% on A4, preferably in color. It covers the complete gravimetric procedure from start to calculation in a single glance.
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