Quiz — correction serie n2 exellent acide base.pd.pdf

Question 1 sur 10 20:00

[{"id":2180,"question":"Quel est le pH d'une solution d'acide chlorhydrique (HCl) de concentration 10^-2 mol\/L ?","option_a":"1","option_b":"2","option_c":"7","option_d":"12","option_e":"","option_f":"","bonne_reponse":"b","explication":"L'acide chlorhydrique est un acide fort qui se dissocie totalement : [H3O+] = 10^-2 mol\/L. Le pH est donc pH = -log([H3O+]) = 2.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"b\", \"options\": {\"a\": \"1\", \"b\": \"2\", \"c\": \"7\", \"d\": \"12\"}}","_debug_options_count":4},{"id":2181,"question":"Un indicateur coloré change de couleur entre pH 4 et pH 6. Peut-il être utilisé pour un dosage d'acide fort par une base forte ?","option_a":"Vrai","option_b":"Faux","option_c":"","option_d":"","option_e":"","option_f":"","bonne_reponse":"a","explication":"Non, car le point d'équivalence d'un dosage acide fort\/base forte se situe à pH = 7. L'indicateur doit changer de couleur autour de ce pH.","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":2182,"question":"La constante d'acidité Ka d'un acide faible est de 10^-5. Quelle est la valeur du pKa ?","option_a":"5","option_b":"10^-5","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^-5\", \"c\": \"-5\", \"d\": \"0,00001\"}}","_debug_options_count":4},{"id":2183,"question":"Lors d'un dosage acido-basique, le volume équivalent est atteint lorsque :","option_a":"Les réactifs sont en proportions stœchiométriques","option_b":"Le pH de la solution est égal à 7","option_c":"La couleur de l'indicateur change","option_d":"La solution devient incolore","option_e":"","option_f":"","bonne_reponse":"a","explication":"Le volume équivalent correspond au moment où les réactifs sont en proportions stœchiométriques, ce qui permet de calculer la concentration inconnue.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"a\", \"options\": {\"a\": \"Les réactifs sont en proportions stœchiométriques\", \"b\": \"Le p","_debug_options_count":4},{"id":2184,"question":"Un acide AH a un pKa de 4,75. Quel est son Ka ?","option_a":"4,75","option_b":"10^-4,75","option_c":"475","option_d":"0,000178","option_e":"","option_f":"","bonne_reponse":"b","explication":"Le Ka est calculé par Ka = 10^(-pKa) = 10^(-4,75) ≈ 1,78 × 10^-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\": \"4,75\", \"b\": \"10^-4,75\", \"c\": \"475\", \"d\": \"0,000178\"}}","_debug_options_count":4},{"id":2185,"question":"La réaction entre l'acide éthanoïque (CH3COOH) et l'eau est totale.","option_a":"Vrai","option_b":"Faux","option_c":"","option_d":"","option_e":"","option_f":"","bonne_reponse":"b","explication":"Faux, l'acide éthanoïque est un acide faible : sa réaction avec l'eau est partielle et limitée par la constante d'acidité Ka.","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":2186,"question":"Quel est le pH d'une solution d'hydroxyde de sodium (NaOH) de concentration 10^-3 mol\/L ?","option_a":"3","option_b":"11","option_c":"7","option_d":"14","option_e":"","option_f":"","bonne_reponse":"b","explication":"NaOH est une base forte qui se dissocie totalement : [OH-] = 10^-3 mol\/L. Le pOH = -log([OH-]) = 3, donc pH = 14 - pOH = 11.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"b\", \"options\": {\"a\": \"3\", \"b\": \"11\", \"c\": \"7\", \"d\": \"14\"}}","_debug_options_count":4},{"id":2187,"question":"Une solution tampon est une solution qui :","option_a":"A un pH constant quelle que soit la dilution","option_b":"Résiste aux variations de pH lors de l'ajout d'acide ou de base","option_c":"Est toujours neutre (pH = 7)","option_d":"Contient uniquement de l'eau","option_e":"","option_f":"","bonne_reponse":"b","explication":"Une solution tampon maintient un pH stable malgré l'ajout modéré d'acide ou de base, grâce à la présence d'un couple acide\/base conjugué.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"b\", \"options\": {\"a\": \"A un pH constant quelle que soit la dilution\", \"b\": \"Résiste aux","_debug_options_count":4},{"id":2188,"question":"La constante d'acidité Ka d'un acide est de 10^-9. Cet acide est-il plus fort ou plus faible que l'acide acétique (Ka = 1,8 × 10^-5) ?","option_a":"Plus fort","option_b":"Plus faible","option_c":"De même force","option_d":"Impossible à comparer","option_e":"","option_f":"","bonne_reponse":"b","explication":"Plus la constante d'acidité Ka est faible, plus l'acide est faible. Ici, 10^-9 \u003C 1,8 × 10^-5, donc l'acide est plus faible que l'acide acétique.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"b\", \"options\": {\"a\": \"Plus fort\", \"b\": \"Plus faible\", \"c\": \"De même force\", \"d\": \"Impo","_debug_options_count":4},{"id":2189,"question":"Lors d'un dosage, si on ajoute trop d'indicateur coloré, cela peut fausser le résultat.","option_a":"Vrai","option_b":"Faux","option_c":"","option_d":"","option_e":"","option_f":"","bonne_reponse":"a","explication":"Faux, l'ajout d'indicateur coloré en quantité raisonnable n'affecte pas le pH de la solution ni le point d'équivalence du dosage.","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}]