on plonge une lame de zinc de masse m=2g dans une solution d'acide chlorhydrique (H+aqueux +cl- aqueux) en excès. au cours de la réaction il y a des formations des ions Zn2+ et production d'un gaz qui donne une donation presence d'une flamme. 1) Ecrire les demi équation redox et l'équation bilan entre l'acide chlorhydrique et le zinc. 2)dresser le tableau d'avancement de la réaction et déterminer l'avancement maximal. 3)calculer le volume de d'hydrogène libéré à la fin de la réaction. 4)calculer la masse m du chlorure de zinc formé à la fin de la réaction. on donne Vm=25 L. mol-1 / M (Zn) =64,5 g. mol-1 / M (Cl) =35.5 g. mol-1

Bose-einstein condensation occurs at what temperature?

Which explanation is true about what happens to a ray of light when it strikes a mirror? a. a light ray is transmitted toward a mirror at a certain angle. the light ray is then reflected by the mirror at an equal angle but in the opposite direction of the transmitted ray. b. an incident ray strikes a mirror at an angle with a line perpendicular to the mirror. the light ray is then reflected at an angle equal to the angle of incidence but on the opposite side of the perpendicular line. c. a reflecting ray strikes a mirror at an angle with a line perpendicular to the mirror. the light ray is then refracted at an angle equal to the angle of the reflecting ray and on the same side of the perpendicular line. d. an incident ray strikes a mirror at an angle with a line parallel to the mirror. the light ray is then transmitted at an angle equal to the angle of incidence but on the opposite side of the parallel line. you so much! : -d take the time to try and answer correctly.

6. using 3 – 4 sentences explain (in your own words) why water expands when it freezes? 7. using your knowledge of colligative properties explain whether sodium chloride or calcium chloride would be a more effective substance to melt the ice on a slick sidewalk. use 3 – 4 sentences in your explanation.