Quiz — Correction série n°9 réaction acide base 2022.pdf

Question 1 sur 10 20:00

[{"id":32010,"question":"Quel est l'acide conjugué de la base NH3 ?","option_a":"NH2-","option_b":"NH4+","option_c":"H2O","option_d":"OH-","option_e":"","option_f":"","bonne_reponse":"b","explication":"L'acide conjugué de NH3 est NH4+, obtenu en ajoutant un proton (H+) à NH3.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"b\", \"options\": {\"a\": \"NH2-\", \"b\": \"NH4+\", \"c\": \"H2O\", \"d\": \"OH-\"}}","_debug_options_count":4},{"id":32011,"question":"Un indicateur coloré change de couleur à pH = 7. Peut-il être utilisé pour titrer un acide fort par une base forte ?","option_a":"Vrai","option_b":"Faux","option_c":"","option_d":"","option_e":"","option_f":"","bonne_reponse":"a","explication":"À l'équivalence d'un titrage acide fort\/base forte, le pH est égal à 7. L'indicateur peut donc être utilisé.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"a\", \"options\": {\"a\": \"Vrai\", \"b\": \"Faux\", \"c\": \"\", \"d\": \"\"}}","_debug_options_count":4},{"id":32012,"question":"Quelle est la formule du pH d'une solution d'acide fort de concentration C ?","option_a":"pH = -log(C)","option_b":"pH = log(C)","option_c":"pH = 14 + log(C)","option_d":"pH = C","option_e":"","option_f":"","bonne_reponse":"a","explication":"Pour un acide fort, le pH se calcule par pH = -log(C), car l'acide se dissocie totalement.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"a\", \"options\": {\"a\": \"pH = -log(C)\", \"b\": \"pH = log(C)\", \"c\": \"pH = 14 + log(C)\", \"d\": ","_debug_options_count":4},{"id":32013,"question":"La constante d'acidité Ka d'un acide faible est de 10^-5. Quel est son pKa ?","option_a":"5","option_b":"10","option_c":"-5","option_d":"0,00001","option_e":"","option_f":"","bonne_reponse":"a","explication":"Le pKa est défini par pKa = -log(Ka). Ici, pKa = -log(10^-5) = 5.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"a\", \"options\": {\"a\": \"5\", \"b\": \"10\", \"c\": \"-5\", \"d\": \"0,00001\"}}","_debug_options_count":4},{"id":32014,"question":"À l'équivalence d'un titrage, le volume de base ajouté est de 10 mL. Le volume initial de l'acide est de 20 mL. Quelle est la concentration de l'acide si celle de la base est de 0,1 mol\/L ?","option_a":"0,05 mol\/L","option_b":"0,1 mol\/L","option_c":"0,2 mol\/L","option_d":"0,025 mol\/L","option_e":"","option_f":"","bonne_reponse":"a","explication":"À l'équivalence, n(acide) = n(base). Donc C(acide) × V(acide) = C(base) × V(base). C(acide) = (0,1 × 10) \/ 20 = 0,05 mol\/L.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"a\", \"options\": {\"a\": \"0,05 mol\/L\", \"b\": \"0,1 mol\/L\", \"c\": \"0,2 mol\/L\", \"d\": \"0,025 mol\/","_debug_options_count":4},{"id":32015,"question":"Un acide faible a un pKa de 4,5. Est-il plus fort qu'un acide de pKa 3,2 ?","option_a":"Vrai","option_b":"Faux","option_c":"","option_d":"","option_e":"","option_f":"","bonne_reponse":"b","explication":"Plus le pKa est faible, plus l'acide est fort. Un pKa de 3,2 indique un acide plus fort qu'un pKa de 4,5.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"b\", \"options\": {\"a\": \"Vrai\", \"b\": \"Faux\", \"c\": \"\", \"d\": \"\"}}","_debug_options_count":4},{"id":32016,"question":"Quelle est la relation entre le pH et le pKa d'une solution tampon ?","option_a":"pH = pKa","option_b":"pH = pKa + log([A-]\/[AH])","option_c":"pH = 14 - pKa","option_d":"pH = pKa × [A-]","option_e":"","option_f":"","bonne_reponse":"b","explication":"La relation de Henderson-Hasselbalch donne pH = pKa + log([A-]\/[AH]) pour une solution tampon.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"b\", \"options\": {\"a\": \"pH = pKa\", \"b\": \"pH = pKa + log([A-]\/[AH])\", \"c\": \"pH = 14 - pKa\"","_debug_options_count":4},{"id":32017,"question":"Un dosage acide-base nécessite un indicateur dont la zone de virage est comprise entre pH 3 et pH 5. Quel indicateur choisir parmi ceux proposés ?","option_a":"Bleu de bromophénol (3,0-4,6)","option_b":"Phénolphtaléine (8,2-10,0)","option_c":"Vert de bromocrésol (3,8-5,4)","option_d":"Rouge de méthyle (4,2-6,3)","option_e":"","option_f":"","bonne_reponse":"c","explication":"Le vert de bromocrésol a une zone de virage (3,8-5,4) qui chevauche la plage 3-5, ce qui le rend adapté.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"c\", \"options\": {\"a\": \"Bleu de bromophénol (3,0-4,6)\", \"b\": \"Phénolphtaléine (8,2-10,","_debug_options_count":4},{"id":32018,"question":"La constante d'acidité Ka d'un acide est de 10^-4. Quelle est la concentration en ions H3O+ d'une solution de cet acide à 0,1 mol\/L ?","option_a":"0,1 mol\/L","option_b":"10^-4 mol\/L","option_c":"10^-3 mol\/L","option_d":"0,01 mol\/L","option_e":"","option_f":"","bonne_reponse":"c","explication":"Pour un acide faible, [H3O+] ≈ √(Ka × C) = √(10^-4 × 0,1) = 10^-3 mol\/L.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"c\", \"options\": {\"a\": \"0,1 mol\/L\", \"b\": \"10^-4 mol\/L\", \"c\": \"10^-3 mol\/L\", \"d\": \"0,01 mo","_debug_options_count":4},{"id":32019,"question":"Un titrage acide-base est réalisé avec une base forte. Le pH à l'équivalence est-il toujours égal à 7 ?","option_a":"Vrai","option_b":"Faux","option_c":"","option_d":"","option_e":"","option_f":"","bonne_reponse":"b","explication":"Le pH à l'équivalence dépend de la force de l'acide et de la base. Pour un acide fort et une base forte, pH = 7. Sinon, il peut être différent.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"b\", \"options\": {\"a\": \"Vrai\", \"b\": \"Faux\", \"c\": \"\", \"d\": \"\"}}","_debug_options_count":4}]