Passover- Eating Karpas at the Seder
One of the stages of the Pesach Seder is "Karpas," the eating of a piece of celery dipped in saltwater. The basic reason for Karpas is to arouse the children's curiosity so that they will ask questions and get involved in the Seder. Additionally, some commentaries have suggested that the letters of the word "Karpas" spell the word "Parech" – backbreaking labor – with an additional letter Samech, which has the numerical value of sixty. The word "Karpas" thus alludes to the 60 groups of ten thousand of Benei Yisrael that were subjected to backbreaking labor during the period of Egyptian bondage.
Of course, before partaking of the Karpas one must recite the Beracha of "Borei Peri Ha'adama." If many people are attending the Seder, it is preferable that one person recites the Beracha on behalf of everybody at the Seder. In such a case, of course, the person reciting the Beracha must have in mind to fulfill the obligation on behalf of everybody else, and they, in turn, must have in mind to fulfill their obligation by listening to his recitation. They would not respond with "Baruch Hu U'varuch Shemo," and would only answer "Amen," and thereby fulfill their obligation vis-à-vis the Beracha. If the person reciting the Beracha will slur or mispronounce the words of the Beracha, then it is certainly preferable for everybody to recite his own Beracha.
Halacha requires that a person eat less than a Ke'zayit of Karpas, since by eating a Ke'zayit one puts himself in a questionable situation with regard to the Beracha Acharona, as it is unclear whether he would have to recite "Borei Nefashot." Chacham Ovadia Yosef rules that one should eat less than 18 grams of Karpas. However, if 18 grams or more, he nevertheless does not recite "Borei Nefashot."
The Ben Ish Chai (Rabbi Yosef Chayim of Baghdad, 1835-1909) writes, based on the Kabbala, that one should ensure that the Ke'ara (Seder plate) remains intact throughout the Seder. Meaning, even if one takes Karpas from the Ke'ara to eat, he must see to it that some Karpas remains on the Ke'ara for the rest of the Seder.
1) If many people are together for the Seder, it is preferable for one individual to recite the Beracha over the Karpas on behalf of the others, provided that he recites it clearly and correctly.
2) One must eat less than 18 grams of Karpas; if one eats this amount or more, he nevertheless does not recite "Borei Nefashot."
3) If one takes Karpas from the Seder plate, he must ensure that some Karpas remains so that the plate stays intact throughout the entire Seder.