Chemistry Help Forum Help with Finding the atomic mass of an unknown metal

 Sep 27th 2011, 01:57 PM #1 kelli Junior Member   Join Date: Sep 2011 Posts: 1 Help with Finding the atomic mass of an unknown metal A 1.00g sample of metal X weighs 1.345 g after complete conversion to the oxide. If the formula for the oxide is X2O3, what is the atomic weight of X? I dont know where to start.
 Sep 27th 2011, 07:02 PM #2 grgrsanjay Super Moderator   Join Date: May 2010 Location: India Posts: 243 Let atomic mass of the unknown metal be M. No.of moles of X present initially is 1/M. According to the formula 1 mole of X reacts with 3/2 moles of Oxygen So,1/M moles of X reacts with 3/2M moles of Oxygen The difference in weights is due to 3/2M moles of oxygen There, you can find the value of M. __________________ If you like my post click Below Forum Rules
 Sep 27th 2011, 11:37 PM #3 Unknown008 Senior Member     Join Date: May 2010 Location: Mauritius Posts: 1,685 Or an alternate method, You know that you started with 1.00 g of the metal and that upon complete oxidation with oxygen, the mass increased to 1.345 g. The 0.345 g is due to the oxygen only, from the general equation for the oxidation of metals. X + O2 ---> XO2 but in this case. 4X + 3O2 ---> 2X2O3 There are no by products and you know that all your metal is still there. So... work out how many moles of oxygen there are in the 0.345 g of oxygen that reacted. You know that in one mole of X2O3 there are 3 moles of O and 2 moles of X. Use proportions to get the number of moles of X. 0.345 g -> ? moles of O Since in 1 mole of X2O3 contains ? moles of O, then there will be (?/3)*2 moles of X. (?/3)*2 moles of X has a mass of 1.00 g, 1 mole of X will have a mass of ??? g (the atomic weight) __________________ Jerry (Working, studying, writing and drawing :3) It is easier to protect your feet with slippers than to cover the earth with carpet. No one can go back and change a bad beginning; but anyone can start now and create a successful ending. If a problem can be solved, no need to worry about it. If it cannot be solved what is the use of worrying? Give a man a fish and you feed him for a day. Teach a man to fish and you feed him for a lifetime. Thank you for leaving a reputation to my post

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