hw question #3

[Kaylee Nezwek 1D]

Hi! For number 3 on the homework, it says, " At a certain temperature, H2 + I2 -> 2HI, Kc = 53.3, at this temperature, 0.700 mol H2 and 0.700 mol I2 were placed in a 1.00 L container to react. What concentration of HI is present at equilibrium?" I set up Kc to be:
53.3 = (2x)^2/(0.7 - x)(0.7 - x)
But I'm a bit confused on how to get the quadratic equation from this. Can someone explain how to get the quadratic equation/what it would be?

[Brennan McGurrr 3C]

You would have to FOIL the denominator then multiply that expression to the other side. This will allow you to set the equation equal to 0 and use the quadratic formula. If you have a graphing calculator, you can graph both sides of the equation and find where they intersect to solve this. I find this method to be faster and easier. Desmos is a good website for an online graphing calculator.

[Nathan Lao 2I]

For this specific K equation, you can actually take the square root of both sides. It would simplify to square root of 53.3 = 2x/(0.7-x) and then you would solve for x from there by rearranging the equation.

[LexyDenaburg_3A]

In this question, how did you set up Kc?

[Sophia Wendin 3L]

multiply out the denominator( (a + b)^2 = a^2 + 2ab + b^2) then cross multiply with 53.3. Move everything to one side so you can find X using the quadratic formula.

[Lung Sheng Liang 3J]

This calculation is simple enough to the point where you don't need to utilize the quadratic formula. You can get the square root of both sides and then solve for x and then to get the concentration for HI multiply that value by 2.

[Shruti Kulkarni 2I]

You can multiply both sides by (0.7 -x)^2 to remove the denominator and then expand each expression to create an equality. Afterward, you can move all the terms to one side and set the equation equal to zero. All that's left is to solve using the quadratic equation or even graphing out the equation to find the zeros.

[Alisa Nagashima 1B]

Hi! Essentially, you just need to rearrange the equation so that it fits the ax² + bx + c = 0 form since it makes it easier to use the quadratic formula. But since the components of the denominator are the same for this equation, it's easier to take the square root of both sides.

[Kaleb Tuliau 3E]

for question 3 when does Oxygen's given equilibrium mole play a role? (if this question makes sense)

[Uyen Trinh 3C]

What helps me get at these chemical equilibrium problems is handwriting everything out. Here is how I did it as well as the way Sapling teaches us to do it. I erased the answers but left all my workings. I hope this helps.

[Gian Boco 2G]

On the right side of the equation, both the numerator and the denominator have a square (once you combine the like terms in the denominator), meaning the entire fraction can be squared. That way, you can square root both sides of the equation and solve with algebra from there.