12. A 15.7 -g sample of sodium carbonate is added to a solution of acetic acid w
ID: 862916 • Letter: 1
Question
12. A 15.7-g sample of sodium carbonate is added to a solution of acetic acid weighing 19.4 g. The two substances react, releasing carbon dioxide gas to the atmosphere. After reaction, the contents of the reaction vessel weighs 28.4 g.
What is the mass of carbon dioxide given off during the reaction?
13. Cadmium metal reacts vigorously with yellow crystals of sulfur to produce a yellow powder of cadmium sulfide. A chemist determines that 112 g of cadmium reacts with 32.1 g of sulfur. How much cadmium sulfide could be produced from 45.4 g of cadmium metal?
18. Pick if it is a chemical or physcial reaction
(a) Pure water is obtained from ocean water by evaporating the water, then condensing it. physical process chemical reaction (b) Mercury is obtained by heating the substance mercury(II) oxide; oxygen is also obtained. physical process chemical reaction (c) Zinc is produced through the electrolysis of aqueous zinc sulfate physical process chemical reaction (d) Gold is obtained from river sand by panning (allowing the heavy metal to settle in flowing water).Explanation / Answer
12.
Na2CO3 + 2CH3COOH = 2CH3COONa + CO2 + H2O
Initially total weight of reaction mixture = 15.7+19.4 = 35.1gm
After reaction weight = 28.4gm
Msss of CO2 given off = Loss in weight of mixture = 35.1-28.4= 6.7gm
13.
112 g of cadmium reacts with 32.1 g of sulfur to give 112+32.1=144.1gm of cadmium sulfide
1gm if cadmium will give 144.1/112gm of cadmium sulfide
45.4gm of cadmium will give 45.4*144.1/112 = 58.4gm of cadmium sulfide
18.
(a) Pure water is obtained from ocean water by evaporating the water, then condensing it.
physical process: No change of molecules
(b) Mercury is obtained by heating the substance mercury(II) oxide; oxygen is also obtained.
chemical reaction: Mercury oxide molecule breaks to give two new molecules.
(c) Zinc is produced through the electrolysis of aqueous zinc sulfate
chemical reaction: zinc sulfate gives pure zinc.
(d) Gold is obtained from river sand by panning (allowing the heavy metal to settle in flowing water).Comment
Physical process
:Gold is in pure form
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