Phosphorus trichloride reacts with chlorine to form phosphorus pentachloride. PCl3(g) + Cl2(g)=
PCl5(g)
0.75 mol of PCl3 and 0.75 mol of Cl2 are placed in a 8.0L reaction vessel at 500K.
What is the equilibrium concentration of the mixture? The value of Kc at 500K is 49.
(6 marks)​

[PCl₃] = [Cl₂] = 0.035M

[PCl₅] = 0.059M

Explanation:

Based on the chemical reaction, Kc is:

Kc = 49 = [PCl₅] / [PCl₃] [Cl₂]

Where [] are the concentrations in equilibrium of each species

The initial concentration of the reactants is:

[PCl₃] = [Cl₂] = 0.75mol / 8.0L =  0.094M

The reactants must be consumed whereas PCl₅ will be produced. That is:

[PCl₃] = [Cl₂] = 0.094M - X

[PCl₅] = X

Where X is the reaction coordinate

Replacing in Kc expression:

49 = [X] / [0.094 - X] [0.094 - X]

49 = [X] / 0.008836 - 0.188 X + X²

0.432964 - 9.212 X + 49 X² = X

0.432964 - 10.212 X + 49 X² = 0

Solving for X

X = 0.059M → Right solution

X = 0.15M → False solution. Will produce negative concentrations

Replacing:

[PCl₃] = [Cl₂] = 0.094M - 0.059M = 0.035M

[PCl₅] = 0.059M

[PCl₃] = [Cl₂] = 0.035M[PCl₅] = 0.059M

Gallium melts near room temperature and has one of the largest  liquid  ranges of any metal, so it has found use in high temperature thermometers.

For cyclohexane compounds drawn in a chair conformation:   -axial bonds are vertical  -equatorial bonds are parallel to two bonds within the ring.  thus, as i assume the chair conformation is drawn:   -the x group is in an axial position, as are the five other vertical bonds.  -three axial bonds are on the top face of the ring  -the other three axial bonds are on the bottom face  the position of the second substituent on each ring carbon is equatorial.  gauche groups must be on an adjacent carbon such as carbon 6 and carbon 2, and also gauche groups are rotated by 60 degrees relative to each other.  drawing the newman projections for c1–c2 and c1–c6 aids in visualizing the groups that are gauche to the y group on c1.  click this link and watch some academic videos that may you more understand the topic