[johnnyjohn993]

A 2.077 g sample of an element, which has an atomic mass between 40amu and 55amu,  reacts with oxygen to form 3.708g of an oxide. Determine the formula of the oxide (and identify the element)

My attempt:
mass of oxygen= 3.708- 2.077 = 1.631g
(I'm using the moles of each substance)

2.077  +  1.631     3.708
------      ------  = --------
  x            32        x + 16
the value of x is an imaginary number (doing the calculations) plz help me ,this is so confusing X(

[Borek]

Adding number of moles of the element to the number of moles of oxygen doesn't yield number of moles of the oxide.

You know mass of oxygen. How many moles is that?

Assuming formula of oxide to be XO, how many moles of the element? What would be its aomic mass?

And what if the formula of the oxide is X₂O?

What other formulas of oxides can you think of?

Each formula yields a possible atomic mass for the element, just compare them to all six possible elements.

[johnnyjohn993]

Adding number of moles of the element to the number of moles of oxygen doesn't yield number of moles of the oxide.

You know mass of oxygen. How many moles is that?

Assuming formula of oxide to be XO, how many moles of the element? What would be its aomic mass?

And what if the formula of the oxide is X₂O?

What other formulas of oxides can you think of?

Each formula yields a possible atomic mass for the element, just compare them to all six possible elements.

At the back of my book it said to be Vanadium is the element. I don't know how to solve this problem, except adding the moles of the reactants to have the same values of moles on the product side because I used it before and able to get a right answer

[Borek]

Follow what I wrote, I asked you questions, try to answer them one by one, in the same order I asked them.

[johnnyjohn993]

Follow what I wrote, I asked you questions, try to answer them one by one, in the same order I asked them.

the following oxides would come up are:  XO , X₂O₃ , XO₂ , X₂O₅ , XO₃ , X₂O₇

moles :

moles of oxigen: 0.05097 mol

XO = (3.708/x+16 ) mol
X₂O₃= (3.708/2x +48)mol
XO₂=  (3.708/x +32)mol
X₂O₅=  (3.708/2x +80)mol
 XO₃ = (3.708/x +48)mol
 X₂O₇= (3.708/2x +112)mol

I don't know how to go further anymore  , just please tell me how you did it ? T_T

[Borek]

XO = (3.708/x+16 ) mol

No, that's not what I asked about.

If the formula of the oxide is XO, number of moles of the metal is identical to number of moles of the oxygen.

If the formula of the oxide is X₂O, number of moles of the metal is twice the number of moles of the oxygen.

If the formula of the oxide is XO₂, number of moles of the metal is half the number of moles of the oxygen.

For each formula calculate number of moles of the metal, and find its atomic mass.