Lead metal is added to 0.100M Cr3+(aq)

Question

Pb(s) + 2Cr3+(aq) -> Pb2+(aq) + Cr2+(aq)

What is [Pb3+] when equilibrium is reached?
What is [Cr2+] when equilibrium is reached?
What is [Cr3+] when equilibrium is reached?

i solved it buh for sum reason am not getting d correct answer =(

Answer 1

Show your work and we will try to find the error.

Answer 2

initail 0.120M 0M 0M
change -2X X 2X
equilbrium (0.120-2X) X 2X

Kc= [Pb^2+] [Cr^2+]/ [Cr3+]

3.2x10^-10 = 4x^3/ (1.20-2x_^2
x= 1.048x10 ^-4

n thn i kno i hv 2 substitude in 'x'
im jus hving probs wid the calculation part..plz help asap..as tis stuff is due 2moro in d morning...HELP!!

Answer 3

You're ok except that the problem says the initial concn is 0.100. Using 0.100 and y (I like to use y so as not to confuse it with the x sign when we write exponents) so I would have
3.2 x 10^-10 = (4y^3)/(0.1-2y)^2.
First we square the denominator. You know how to do that by the FOIL method.
0.01 - 0.4y + 4y^2) and the equation becomes
4y^3 = 3.2 x 10^-10*(0.01 -0.4y + 4y^2)
Multiply the right side and move everyting to the left side. If you have a calculator you can solve the cubic equation but you can take a shortcut and set the cubed term (the 4y^3) = to the constant. You'll get almost the same answer

Answer 4

im still not getting the answer right!!! =(
n it ws my mistake...the concentration is 0.120M

Answer 5

it ok how u doin