Quiz — Serie 12- acide-base + pH.pdf

Question 1 sur 5 10:00

[{"id":838,"question":"Quel est l’ion caractéristique d’un acide selon la théorie de Brønsted-Lowry ?","option_a":"A. H+","option_b":"B. OH-","option_c":"C. H3O+","option_d":"D. Cl-","option_e":"","option_f":"","bonne_reponse":"C","explication":"Selon Brønsted-Lowry, un acide est une espèce chimique capable de céder un proton H+. En solution aqueuse, ce proton s’associe à une molécule d’eau pour former l’ion H3O+.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0},{"id":839,"question":"Quel est le pH d’une solution de HCl de concentration 0,01 mol\/L ?","option_a":"A. 1","option_b":"B. 2","option_c":"C. 7","option_d":"D. 12","option_e":"","option_f":"","bonne_reponse":"B","explication":"HCl est un acide fort qui se dissocie totalement. [H3O+] = 0,01 mol\/L = 10^-2 mol\/L. pH = -log([H3O+]) = -log(10^-2) = 2.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0},{"id":840,"question":"Quel indicateur coloré est adapté pour un dosage d’acide fort par une base forte ?","option_a":"A. Phénolphtaléine (pKa = 9,3)","option_b":"B. Bleu de bromothymol (pKa = 7,1)","option_c":"C. Rouge de méthyle (pKa = 5,0)","option_d":"D. Bleu de thymol (pKa = 8,9)","option_e":"","option_f":"","bonne_reponse":"B","explication":"Le bleu de bromothymol change de couleur autour de pH = 7,1, ce qui correspond au pH à l’équivalence d’un dosage acide fort\/base forte.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0},{"id":841,"question":"Une solution a un pH de 4. Quelle est sa concentration en ions H3O+ ?","option_a":"A. 10^-4 mol\/L","option_b":"B. 10^-10 mol\/L","option_c":"C. 4 mol\/L","option_d":"D. 0,4 mol\/L","option_e":"","option_f":"","bonne_reponse":"A","explication":"pH = -log([H3O+]) ⇒ [H3O+] = 10^-pH = 10^-4 mol\/L.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0},{"id":842,"question":"Quelle est la formule de la constante d’acidité Ka d’un acide AH ?","option_a":"A. Ka = [A-][H3O+]\/[AH]","option_b":"B. Ka = [AH]\/[A-][H3O+]","option_c":"C. Ka = [H3O+]\/[AH]","option_d":"D. Ka = [A-][OH-]\/[AH]","option_e":"","option_f":"","bonne_reponse":"A","explication":"La constante d’acidité Ka est définie par l’équilibre AH + H2O ⇌ A- + H3O+, soit Ka = [A-][H3O+]\/[AH].","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0}]