Need to identify mysterious element

[jacker2011]

Homework Statement

An element X forms both a dicholride( XCl2) and tetrachloride(XCl4). Treatment of 10.0g of XCl2 with excess forms 12.55g of XCl4. Calculate Atomic Mass of X and Identify X

Homework Equations

no equation needed...but urgent

The Attempt at a Solution

i try subtracting 12.55g of XCL4 with 10.0g of 10.0g of XCL2
and i am lost at what is the EXCESS, is that CL2 ?

if it is...then i have 2.55g/ 71g CL2 = 0.359mole of CL2. basically i am lost

 

[dextercioby]

Do you get the equation

$$\frac{10}{x+71}=\frac{12.55}{x+142}$$ ?

 

[jacker2011]

thank you, i never realize i just have to use cross multiply. i see ur work as x+CL2(71) = x+Cl4(142)