Wolframul pur poate fi obţinut prin reducerea oxidului de Wolfram (VI) cu: a) Zinc; b)oxid de carbon (II); c) aluminiu; d) hidrogen.

Alcătuieşte ecuaţia reacţiei pentru una din variante, egaleaz-o prin metoda bilanţului electronic, indică oxidantul şi reducătorul.

E-r

B-ē:

Asample contains 16.75 g of the radioisotope u-236 and 50.25 g of its daughter isotope, th-232. how long did it take for decay to take place if one half-life of u-236 is 23 million years? 46 million years 69 million years 92 million years 115 million years

1. suppose a reaction mixture, when diluted with water, afforded 300 ml of an aqueous solution of 30 g of the reaction product malononitrile [ch2(cn)2], which is to be isolated by extraction with ether. the solubility of malononitrile in ether at room temperature is 20.0 g/100 ml, and in water is 13.3 g/100 ml. what weight of malononitrile would be recovered by extraction with (a) three 100-ml portions of ether and (b) one 300-ml portion of ether? suggestion: for each extraction, let x equal the weight extracted into the ether layer. in part (a), the concentration in the ether layer is x/100 and in the water layer is (30 x)/300; the ratio of these quantities is equal to k 20/13.3.

What determines the average kinetic energy of the particles in a gas? a. the number of collisions b. the number of particles c. the size of the particles d. the temperature