Les acides et les bases : définitions, pH et titrages

Question 1 sur 10 10:00

[{"id":48171,"question":"Quel est l'acide conjugué de l'ion HCO3- ?","option_a":"H2CO3","option_b":"CO3^2-","option_c":"H3O+","option_d":"OH-","option_e":"","option_f":"","bonne_reponse":"A","explication":"L'acide conjugué d'une base est obtenu en ajoutant un proton (H+). HCO3- + H+ → H2CO3.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0},{"id":48172,"question":"Le pH d'une solution d'acide chlorhydrique (HCl) de concentration 0,01 mol\/L est égal à :","option_a":"2","option_b":"1","option_c":"12","option_d":"7","option_e":"","option_f":"","bonne_reponse":"A","explication":"pH = -log[H3O+]. [H3O+] = 0,01 mol\/L → pH = -log(0,01) = 2.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0},{"id":48173,"question":"Une base selon Brønsted-Lowry est une espèce chimique capable de :","option_a":"Vrai","option_b":"Faux","option_c":"","option_d":"","option_e":"","option_f":"","bonne_reponse":"A","explication":"Une base est une espèce capable de capter un proton (H+), selon la définition de Brønsted-Lowry.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0},{"id":48174,"question":"Quel est le pH d'une solution de soude (NaOH) de concentration 0,001 mol\/L ?","option_a":"3","option_b":"11","option_c":"14","option_d":"7","option_e":"","option_f":"","bonne_reponse":"B","explication":"NaOH est une base forte : [OH-] = 0,001 mol\/L → pOH = 3 → pH = 14 - 3 = 11.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0},{"id":48175,"question":"Lors d'un titrage acido-basique, le point d'équivalence correspond à :","option_a":"Un changement de couleur de l'indicateur","option_b":"L'égalité des quantités de matière d'acide et de base","option_c":"Un pH de 7","option_d":"La fin de la réaction","option_e":"","option_f":"","bonne_reponse":"B","explication":"Le point d'équivalence est atteint lorsque les quantités de matière d'acide et de base sont stœchiométriquement égales.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0},{"id":48176,"question":"La réaction entre l'acide sulfurique (H2SO4) et l'eau donne :","option_a":"Vrai","option_b":"Faux","option_c":"","option_d":"","option_e":"","option_f":"","bonne_reponse":"A","explication":"H2SO4 est un acide fort qui se dissocie totalement en 2H+ et SO4^2- en solution aqueuse.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0},{"id":48177,"question":"Quel indicateur coloré utilise-t-on pour un titrage d'acide fort par une base forte ?","option_a":"Phénolphtaléine","option_b":"Bleu de bromothymol","option_c":"Rouge de méthyle","option_d":"Vert de bromocrésol","option_e":"","option_f":"","bonne_reponse":"B","explication":"Le bleu de bromothymol change de couleur autour de pH = 7, idéal pour les titrages acide fort\/base forte.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0},{"id":48178,"question":"Le pKa d'un couple acide\/base est une mesure de :","option_a":"La force de l'acide","option_b":"Le pH de la solution","option_c":"La concentration en ions H3O+","option_d":"La température de dissociation","option_e":"","option_f":"","bonne_reponse":"A","explication":"Le pKa indique la force d'un acide : plus le pKa est faible, plus l'acide est fort.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0},{"id":48179,"question":"Une solution a un pH de 4. Elle est donc :","option_a":"Vrai","option_b":"Faux","option_c":"","option_d":"","option_e":"","option_f":"","bonne_reponse":"A","explication":"Un pH de 4 indique une solution acide (pH \u003C 7).","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0},{"id":48180,"question":"Quelle est la concentration en ions H3O+ d'une solution de pH = 3 ?","option_a":"10^-3 mol\/L","option_b":"10^3 mol\/L","option_c":"3 mol\/L","option_d":"0,001 mol\/L","option_e":"","option_f":"","bonne_reponse":"A","explication":"pH = -log[H3O+] → [H3O+] = 10^-pH = 10^-3 mol\/L.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0}]