Question

Q1) why did you have two different indicators in this expriment rather than just phenolphthalein or just methyl orange?

Q2) Was it necessary to use a dry Erlenmeyer flask to prepare the unknown sample for titration or was it okay if the flask was left slightly wet with distilled water after you washed it and before you placed your sample in it? Explain.

Q3) Using your textbook as a resource, suggest two alternative pH indicators that could be used for this experiment instead of phenolphthalein and methyl orange. Explain your choice.

Q4) If the pH indicator used for the titration in step 1 changed color at a lower pH than phenolphthalein what effect would it have on the mass and what percent of the sodium carbonate determined in this experiment? Explain.

Answer 1

1) we have two different indicators in this expriment rather than just phenolphthalein or just methyl orange

because these two indicators have different pH range

Methyl Orange goes from red to orange at pH 3 to 4
Phenolphthalien goes from clear to red at pH 9 to 10

2) Yes,  it was necessary to use a dry Erlenmeyer flask to prepare the unknown sample for titration or was it okay if the flask was left slightly wet with distilled water after you washed it and before you placed your sample in it

IN presence of water the concerntration of unkown solution may vary as its concentration may change .

and we get incorrect reading .

3) the two alternative pH indicators that could be used for this experiment instead of phenolphthalein and methyl orange are those who also have pH range similar to these indicators

in place of Methyl Orange pH 3 to 4   we use Bromocresol green which having pH range 3.8 - 4.6

colour change is yellow to blue

in place of Phenolphthalien  pH 9 to 10 we can use Thymolpthalein which having pH range 9.3 - 10.5

colour change is colourless to blue