Quiz — Serie Chimie 06.12.2021 Dosage Manganimétrie.pdf

Question 1 sur 10 20:00

[{"id":68056,"question":"Quel est l'ion oxydant utilisé en manganimétrie ?","option_a":"MnO₄⁻","option_b":"Cr₂O₇²⁻","option_c":"I⁻","option_d":"Fe²⁺","option_e":"","option_f":"","bonne_reponse":"a","explication":"L'ion permanganate (MnO₄⁻) est l'oxydant standard en manganimétrie, de couleur violette en solution.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"a\", \"options\": {\"a\": \"MnO₄⁻\", \"b\": \"Cr₂O₇²⁻\", \"c\": \"I⁻\", \"d\": \"Fe²⁺\"}}","_debug_options_count":4},{"id":68057,"question":"En milieu acide, l'ion MnO₄⁻ se réduit en :","option_a":"Mn²⁺","option_b":"MnO₂","option_c":"MnO₄²⁻","option_d":"Mn","option_e":"","option_f":"","bonne_reponse":"a","explication":"En milieu acide, MnO₄⁻ se réduit en Mn²⁺ (ion manganèse(II)), de couleur rose pâle.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"a\", \"options\": {\"a\": \"Mn²⁺\", \"b\": \"MnO₂\", \"c\": \"MnO₄²⁻\", \"d\": \"Mn\"}}","_debug_options_count":4},{"id":68058,"question":"Vrai ou Faux ? La manganimétrie permet de doser des ions ferreux (Fe²⁺).","option_a":"Vrai","option_b":"Faux","option_c":"","option_d":"","option_e":"","option_f":"","bonne_reponse":"a","explication":"Vrai. Les ions Fe²⁺ sont oxydés en Fe³⁺ par MnO₄⁻, ce qui permet leur dosage par titrage.","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":68059,"question":"Quel indicateur est utilisé en manganimétrie ?","option_a":"Phénolphtaléine","option_b":"L'indicateur n'est pas nécessaire","option_c":"Bleu de bromophénol","option_d":"Vert de bromocrésol","option_e":"","option_f":"","bonne_reponse":"b","explication":"En manganimétrie, le changement de couleur du MnO₄⁻ (violet à incolore) sert d'indicateur naturel.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"b\", \"options\": {\"a\": \"Phénolphtaléine\", \"b\": \"L'indicateur n'est pas nécessaire\", \"c","_debug_options_count":4},{"id":68060,"question":"L'équation d'oxydoréduction en milieu acide est : MnO₄⁻ + 8H⁺ + ne⁻ → Mn²⁺ + 4H₂O. Que vaut n ?","option_a":"1","option_b":"3","option_c":"5","option_d":"7","option_e":"","option_f":"","bonne_reponse":"c","explication":"L'équilibrage donne n = 5, car Mn passe de +VII à +II (gain de 5 électrons).","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"c\", \"options\": {\"a\": \"1\", \"b\": \"3\", \"c\": \"5\", \"d\": \"7\"}}","_debug_options_count":4},{"id":68061,"question":"Vrai ou Faux ? Le titrage manganimétrique doit être réalisé à chaud.","option_a":"Vrai","option_b":"Faux","option_c":"","option_d":"","option_e":"","option_f":"","bonne_reponse":"a","explication":"Vrai. La réaction est plus rapide à chaud, ce qui améliore la précision du titrage.","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":68062,"question":"Quelle est la couleur de la solution à l'équivalence en manganimétrie ?","option_a":"Rose pâle persistante","option_b":"Incolore","option_c":"Jaune","option_d":"Vert","option_e":"","option_f":"","bonne_reponse":"a","explication":"À l'équivalence, un excès de MnO₄⁻ colore la solution en rose pâle, indiquant la fin du titrage.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"a\", \"options\": {\"a\": \"Rose pâle persistante\", \"b\": \"Incolore\", \"c\": \"Jaune\", \"d\": \"Ver","_debug_options_count":4},{"id":68063,"question":"Quel est le rôle de l'acide sulfurique dans un titrage manganimétrique ?","option_a":"Oxydant","option_b":"Réducteur","option_c":"Milieu réactionnel acide","option_d":"Indicateur","option_e":"","option_f":"","bonne_reponse":"c","explication":"L'acide sulfurique fournit les ions H⁺ nécessaires pour équilibrer l'équation d'oxydoréduction en milieu acide.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"c\", \"options\": {\"a\": \"Oxydant\", \"b\": \"Réducteur\", \"c\": \"Milieu réactionnel acide\", \"d","_debug_options_count":4},{"id":68064,"question":"Vrai ou Faux ? La manganimétrie permet de doser des ions chlorure (Cl⁻).","option_a":"Vrai","option_b":"Faux","option_c":"","option_d":"","option_e":"","option_f":"","bonne_reponse":"b","explication":"Faux. Les ions Cl⁻ ne sont pas dosés par manganimétrie car ils interfèrent avec la réaction (formation de Cl₂).","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":68065,"question":"Calculez la concentration d'une solution de Fe²⁺ si 20 mL de cette solution sont titrés par 15 mL de KMnO₄ à 0,02 mol\/L.","option_a":"0,015 mol\/L","option_b":"0,03 mol\/L","option_c":"0,06 mol\/L","option_d":"0,075 mol\/L","option_e":"","option_f":"","bonne_reponse":"b","explication":"D'après l'équation : 5Fe²⁺ + MnO₄⁻ + 8H⁺ → 5Fe³⁺ + Mn²⁺ + 4H₂O. n(MnO₄⁻) = 0,02 × 0,015 = 3×10⁻⁴ mol. n(Fe²⁺) = 5 × 3×10⁻⁴ = 1,5×10⁻³ mol. [Fe²⁺] = 1,5×10⁻³ \/ 0,02 = 0,03 mol\/L.","points":1,"type":"qcm","actif":1,"section_id":null,"ordre":0,"_debug_answer_data_type":"string","_debug_answer_data_preview":"{\"correct\": \"b\", \"options\": {\"a\": \"0,015 mol\/L\", \"b\": \"0,03 mol\/L\", \"c\": \"0,06 mol\/L\", \"d\": \"0,075 m","_debug_options_count":4}]