메틸 오렌지를 이용한 산염기 적정
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강산으로 약염기 적정하기
목표
메틸 오렌지를 지시약으로 사용하여 염산으로 탄산나트륨 용액을 적정하고 농도를 결정한다. 산성 종점에 적합한 지시약 선택을 학습한다.
배경
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.
안전 경고
- HCl is corrosive — avoid skin contact
- Wear safety goggles throughout
- Methyl orange is an azo dye — avoid contact with skin
필수 개인 보호 장비
재료
-
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)
장비
실험 절차
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).
예상 결과
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.
정리
Neutralize waste solutions. Rinse all glassware with distilled water. Drain and rinse the burette.
세부 정보
- 카테고리
- Titrations
- 난이도
- Intermediate (High School)
- 소요 시간
- 40 분
- 예상 비용
- $12.00
- 단계
- 7
- 재료
- 4