General Chemistry Answers

Nitrogen monoxide reacts with oxygen to form nitrogen dioxide.

2NO(g)    +    O2(g)            2NO2(g)

At 1000K the equilibrium constant is 1.60. A mixture of these gases at 1000K contains 0.080mol L-1 oxygen, 0.050mol L-1 nitrogen monoxide and 0.010mol L-1 nitrogen dioxide.

Is this mixture at equilibrium? If not at equilibrium, which direction would the reaction need to shift to achieve equilibrium?

Iron (III) ions, Fe3+, react with thiocyanate ions, SCN-, in a reversible reaction to form a red solution. Which changes to the equilibrium will make the solution go red?

  Fe3+(aq) + SCN-(aq)               [FeSCN]2+(aq)  ∆ H  = +ve

Yellow                                                        Red

I  - Increasing the temperature II  -  Adding FeCl3 III  -  Adding a catalyst

A.   I and II only B.   I and III only

C.   II and III only D.   I, II and III

Consider the following equilibrium:

2NO(g)     +     O2(g)          2NO2(g) Keq   =   1.5

0.800 mole NO, 0.600 moles O2, and 0.400 moles NO2 are placed in a vessel that 2.0 L. 

(i). Show by calculation that the initial combination of all species does not represent an equilibrium?

(ii). What will happen to [O2] as equilibrium is approached?

A mixture was prepared using 1.00mol of propanoic acid, 2.00mol of ethanol and 5.00mol of water. At a given temperature, the mixture was left to reach equilibrium according to the following equation.

CH3CH2COOH  +  CH3CH2OH     CH3CH2COOCH2CH3  +  H2O       ∆Hο = –22kJ mol–1

The equilibrium mixture contained 0.54mol of the ester ethyl propanoate.

(a)(i). Calculate the amounts, in moles, of propanoic acid, of ethanol and of water in this equilibrium mixture.

(ii). Write an expression for the equilibrium constant, Kc, for this equilibrium.

(iii). Calculate a value for Kc for this equilibrium at this temperature. Explain why this Kc value has no units.

(b). For this equilibrium, predict the effect of an increase in temperature on each of the following.

(i). the amount, in moles, of ester at equilibrium

(ii). the time taken to reach equilibrium

(iii). the value of Kc

Consider the reaction

2A   +   B         C   +   3D

The concentration of each of the species at equilibrium is 

[A]   =   0.6M, [B]   =   0.5M, [C]   =   2M and [D]  =  3M

Calculate the value for the equilibrium constant.

The standard enthalpy of formation, ΔHf for O3(g) is + 142kJ mol–1. In which one of the following would both the changes shown increase the amount of O2 gas in an equilibrium mixture containing only O2(g) and O3(g)?

A. increasing the temperature and increasing the pressure

B. increasing the temperature and decreasing the pressure

C. decreasing the temperature and increasing the pressure

D. decreasing the temperature and decreasing the pressure

 A sample of chlorine gas was sealed in a tube, heated and an equilibrium was established.

Cl2(g)     ⇌     2Cl(g)

Which one of the following is not true?

A. The concentration of chlorine atoms remains the same when a catalyst is added to the tube.

B. Increase in temperature causes an increase in the concentration of chlorine atoms.

C. Increase in pressure causes an increase in the concentration of chlorine atoms relative to chlorine molecules.

D. Addition of more chlorine gas to the tube causes an increase in the concentration of chlorine atoms.

Write equilibrium constant expressions for each of the following equations.

(i). 2S02(g)    +    02(g)            2S03(g)

(ii) P4(s)    +     6H2(g)          4PH3(g)

(iii). 4NH3(g)    +     702(g)           4N02(g)    +     6H20(g)

Write the expression for the equilibrium constant for the following reaction.

2Cl2(g)    +    2H2O(l)           4HCl(g)    +    O2(g)

A sample neon has a volume of 5400ml at 29.5 C. At what temperature would the gas occupy a volume of 1000ml?