| Author | Message | ||
     981099 Username: 981099 Registered: 04-2003 |
methyl orange , in acid is what colour ? orange or red ? | ||
| 迪 Username: 981001 Registered: 04-2003 |
red | ||
| Chio U Kim Username: cuk Registered: 04-2003 |
pH > 4.4 yellow 4.4 > pH > 3.2 orange pH < 3.2 red | ||
| Samson Username: 981125 Registered: 04-2003 |
咁咪test唔到幾時係中性囉? | ||
| Chio U Kim Username: cuk Registered: 04-2003 |
Remember that only the neutralization of a strong acid with a strong alkali can result in a neutral solution with pH 7. In this case, methyl orange is not a suitable indicator for end point detection because there is not colour change at pH 7. However, for the titration of a strong acid (e.g. HCl) against a weak alkali (e.g. NaHCO3), the pH value of the reaction mixture at the end point is always < 7. And a colour change from yellow to orange will be observed if methyl orange is used as an indicator. If the end point is overshot, the reaction mixture will appear red. Sometimes, further colour change from orange to red can be brought about by just adding one or two more drops of acid and this overshooting can be tolerated. |