Chuẩn Độ Axit-Bazơ với Metyl Da Cam
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Chuẩn độ bazơ yếu bằng axit mạnh
Mục tiêu
Xác định nồng độ dung dịch natri cacbonat bằng cách chuẩn độ với axit clohydric dùng metyl da cam làm chỉ thị, phù hợp cho điểm tương đương axit.
Bối cảnh
Methyl orange changes color at pH 3.1-4.4 (red to yellow), making it suitable for titrations where the equivalence point is in the acidic range. Sodium carbonate reacts with HCl in a two-step process: first forming NaHCO₃, then NaCl + H₂O + CO₂. Methyl orange detects the second equivalence point.
Cảnh báo an toàn
- HCl is corrosive — avoid skin contact
- Wear safety goggles throughout
- Methyl orange is an azo dye — avoid contact with skin
PPE cần thiết
Vật liệu
-
Sodium carbonate (Na₂CO₃) (100 mL)Unknown concentration
-
Hydrochloric acid (HCl) (100 mL)0.1M standardized
-
Methyl orange indicator (5 mL)0.1% solution
-
Distilled water (200 mL)
Thiết bị
Quy trình
Rinse the burette with HCl solution, then fill it to the 0 mL mark.
Pipette 25.0 mL of sodium carbonate solution into the Erlenmeyer flask.
Add 2-3 drops of methyl orange indicator. The solution should appear yellow (alkaline).
Add HCl slowly while swirling. Watch for the color change from yellow through orange.
Near the endpoint, add drop by drop until the solution changes from yellow to a persistent orange/salmon color.
Record the volume of HCl used. Repeat for concordant results.
Calculate the concentration of Na₂CO₃ considering the 1:2 stoichiometry (Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂).
Kết quả dự kiến
The endpoint shows a clear transition from yellow to a persistent orange/salmon color. The volume ratio should confirm the 1:2 molar ratio of carbonate to acid.
Dọn dẹp
Neutralize waste solutions. Rinse all glassware with distilled water. Drain and rinse the burette.
Chi tiết
- Danh mục
- Titrations
- Độ khó
- Intermediate (High School)
- Thời gian
- 40 phút
- Chi phí ước tính
- $12,00
- Số bước
- 7
- Vật liệu
- 4