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When chromium metal reacts with chlorine gas, a violet solid with the formula CrCl3 is formed: 2 Cr + 3 Cl2 --?
When chromium metal reacts with chlorine gas, a violet solid with the formula CrCl3 is formed: 2 Cr + 3 Cl2 --> 2 CrCl3 How many grams of Cr are needed to produce 200. g of CrCl3?
2 Answers
- Roger SLv 71 decade agoFavourite answer
The first thing to understand is what a mole is. It is just a number chemists use to express weight. This many atoms of any element in the periodic table equals its atomic weight. Molecular weight is the sum of atomic weight.
The next thing is to write a balanced equation describing the reaction. Balanced means there are equal numbers of atoms on each side.
2Cr + 3Cl2 -> 2CrCl3
Since moles are just numbers, the number of molecules in the equation is also equal to the number of moles. To find the amounts, first express all the weight in terms of moles. 52 + 3*35.5 = 158.5 grams/mole for CrCl3. 200 grams / (158.5 grams/mole) = 1.26 moles CrCl3. Since the ratio of Cr to CrCr3 is the same, this means 1.26 moles of Cr are also needed. (1.26 moles)*(52 grams/mole) = 65.6 grams of Chromium.
It's really quite simple once one understands everything, but the concept of molarity is the worst taught subject in all science.
Source(s): I'm a chemist!