How many moles of hi are present at equilibrium when 2.0 moles of h2 is mixed with 1.0 moles of i2 in a 0.50 l container and allowed to react at 448oc. at this temperature k = 50.

1.9 mol.

Explanation:

H₂ + I₂ → 2HI,

The initial concentrations:

The equilibrium constant (K) = [HI]²/[H₂][I₂],

Write down the equation and the start concentrations. Let (x) be the finish concentrations:

                 H₂       +      I₂     →     2HI

start:       4.0 M        2.0 M         0 M  

finish:     4.0-x         2.0-x           2x

∴ The equilibrium constant (K) = [HI]²/[H₂][I₂] = (2x)²/(4.0 - x)(2.0 - x).

∴ 50 = (2x)²/(4.0 - x)(2.0 - x).

∴ 50 = (4x²)/(8.0 - 6.0 x + x²).

∴ 400 - 300 x + 50 x² = 4x².

∴ 46x² - 300 x + 400 = 0    (standard form)

Use the quadratic equation to solve for (x):

x = (- b ± √(b² - 4ac))/(2a),  

In this case a = +46, b = -300 and c = +400.

x = (+ 300) ± √((- 300)² - 4 (46)(400))/(2 (46))

x = (+ 300) ± √(9000 - 73600)/(92)

x = (+ 300) ± 127)/(92)

∴ x = 4.7 and 1.9

When  x = 4.7 is not possible, because 4.0 - 4.7 (the concentration of H2 would be negative).

So, x = 1.9.

∴ [HI] = 2x

If x = 1.9,

∴ [HI] = 2(1.9) = 3.8 mol/L.

∵ [HI] = no. of moles/volume of the container.

∴ no. of moles of (HI) = [HI]*volume of the container = (3.8 mol/L)(0.5 L) = 1.9 mol.

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.