about the relationship between Kc and Kp is
SUB: Chemistry
CLASS: 11th
MM: 40
General instructions
Question no.01 to 10 carry one marks.
Question no.11 to 14 carry two marks.
Question no. 15 to 17 carry three marks.
Question no.18 to 19 carry four marks.
Question no. 20 carry five marks.
SECTION A- (1M)
Q.1. We know about the relationship between Kc and Kp is
Kp = Kc (RT)∆n
What will be the value of ∆n for the reaction
NH4Cl (s) → NH3 (g) + HCl (g)
(i) 1
(ii) 0.5
(iii) 1.5
(iv) 2
Q.2. In the case of the reaction
H2(g) + I2(g) → 2HI (g),
the standard free energy is given as
∆G > 0.
The equilibrium constant (K) will be ___
(i) K = 0
(ii) K > 1
(iii) K = 1
(iv) K < 1
Q.3.Which of the following is not the general feature of equilibria involving physical processes?
(i) Equilibrium is possible only in the closed system at the given temperature.
(ii) All measurable properties of the given system remain constant.
(iii) All the physical processes stop at equilibrium.
(iv) The opposing process occurs at the same rate, and there is the dynamic, however stable condition.
Q.4.PCl5, PCl3, and Cl2 are at equilibrium at 500K in the closed container, and their concentrations are given as 0.8 × 10–3mol L–1, 1.2 × 10–3 mol L–1, and 1.2 × 10–3 mol L–1 respectively. The value of Kc for the given reaction
PCl5 (g) PCl3 (g) + Cl2 (g) will be,
(i) 1.8 × 103mol L–1
(ii) 1.8 × 10–3
(iii) 1.8 × 10–3 L moL–1
(iv) 0.55 × 104
Q.5. The acidity of the compound BF3 could be explained based on which among the following concepts?
(i) Arrhenius’s concept
(ii) Bronsted Lowry’s concept
(iii) Lewis’s concept
(iv) Bronsted Lowry as well as Lewis’s concept.
Q.6. Which of the following is not a redox reaction?
(a) CaCO3 → CaO + CO2
(b) O2 + 2H2 → 2H2O
(c) Na + H2O → NaOH + 1/2H2
(d) MnCl3 → MnCl2 + 1/2 Cl2
Q.7.The most powerful oxidising agent among the following is:
(a) H2SO4
(b) H3BO3
(c) HPO3
(d) H3PO4
Q.8.The oxidation number of Cr in K2Cr2O7 is:
(a) -6
(b) +6
(c) +2
(d) -2
Q9. Consider the following reaction:
Zn + Cu2+ → Zn2+ + Cu
With reference to the above, which one of the following is the correct statement?
(a) Zn is reduced to Zn2+ ions.
(b) Zn is oxidised to Zn2+ ions.
(c) Zn2+ ions are oxidised to Zn.
(d) Cu2+ ions are oxidized to Cu.
Q.10. Reduction never involves:
(a) gain of electrons
(b) decrease in oxidation number
(c) loss of electrons
(d) decrease in valency of electropositive component
SECTION- B (2M EACH)
Q.11. The value of Kc for the given reaction
2HI (g) ⇋ H2 (g) + I2 (g) is 1 × 10-4
At the given time, the composition of the reaction mixture is given as follows;
[HI] =2 × 10-5 mol, [H2] =1 × 10-5 mol as well as [I2] =1 × 10-5 mol.
Q.12. Predict whether the solutions for the following salts are neutral, acidic or basic: NaCl, KBr, NH4NO3, and KF.
In which direction would the reaction proceed?
Q.13. Calculate the oxidation number of phosphorus in the following species.
(a) HPO32- and
(b) PO43-
Q.14 Balance the following redox reactions by half reaction method
Cr2O7 2-- + Fe2+(aq.) → Cr3+(aq.) + Fe3+ (aq.) (in acidic solution)
SECTION- C (3M EACH)
Case Study 1:
The idea of oxidation number has been invariably applied to define oxidation, reduction, oxidising agent (oxidant), reducing agent (reductant) and the redox reaction. To summarise, we may say that:
Oxidation: An increase in the oxidation number of the element in the given substance.
Reduction: A decrease in the oxidation number of the element in the given substance.
Oxidising agent: A reagent which can increase the oxidation number of an element in a given substance. These reagents are called as oxidants also.
Reducing agent: A reagent which lowers the oxidation number of an element in a given substance. These reagents are also called as reductants.
Redox reactions: Reactions which involve change in oxidation number of the interacting species.
Types of Redox Reactions
1.) Combination reactions -A combination reaction may be denoted in the manner:
A + B → C
Either A and B or both A and B must be in the elemental form for such a reaction to be a redox reaction. All combustion reactions, which make use of elemental dioxygen, as well as other reactions involving elements other than dioxygen, are redox reactions. Some important examples of this category are:
2.) Decomposition reactions- Decomposition reactions are the opposite of combination reactions. Precisely, a decomposition reaction leads to the breakdown of a compound into two or more components at least one of which must be in the elemental state.
Examples of this class of reactions are:
It may carefully be noted that there is no change in the oxidation number of hydrogen in methane under combination reactions and that of potassium in potassium chlorate in reaction. This may also be noted here that all decomposition reactions are not redox reactions. For example, decomposition of calcium carbonate is not a redox reaction.
3.) Displacement reactions- In a displacement reaction, an ion (or an atom) in a compound is replaced by an ion (or an atom) of another element. It may be denoted as:
X + YZ → XZ + Y
Displacement reactions fit into two categories: metal displacement and non-metal displacement.
(a) Metal displacement: A metal in a compound can be displaced by another metal in the uncombined state. Metal displacement reactions find many applications in metallurgical processes in which pure metals are obtained from their compounds in ores.
(b) Non-metal displacement: The non-metal displacement redox reactions include hydrogen displacement and a rarely occurring reaction involving oxygen displacement. All alkali metals and some alkaline earth metals (Ca, Sr, and Ba) which are very good reductants, will displace hydrogen from cold water. Many metals, including those which do not react with cold water, are capable of displacing hydrogen from acids. Dihydrogen from acids may even be produced by such metals which do not react with steam. Cadmium and tin are the examples of such metals.
4.) Disproportionation reactions – Disproportionation reactions are a special type of redox reactions. In a disproportionation reaction an element in one oxidation state is simultaneously oxidised and reduced. One of the reacting substances in a disproportionation reaction always contains an element that can exist in at least three oxidation states. The element in the form of reacting substance is in the intermediate oxidation state; and both higher and lower oxidation states of that element are formed in the reaction. The decomposition of hydrogen peroxide is a familiar example of the reaction, where oxygen experiences disproportionation.
Here the oxygen of peroxide, which is present in –1 state, is converted to zero oxidation state in O2 and decreases to –2 oxidation state in H2O.
Q.15.
(i) In … an ion (or an atom) in a compound is replaced by an ion (or an atom) of another element.
a) displacement reaction
b) decomposition reaction
c) disproportionation reaction
d) combination reaction
ii) … leads to the breakdown of a compound into two or more components at least one of which must be in the elemental state.
a) displacement reaction
b) decomposition reaction
c) disproportionation reaction
d) combination reaction
iii) In …. an element in one oxidation state is simultaneously oxidised and reduced.
a) displacement reaction
b) decomposition reaction
c) disproportionation reaction
d) combination reaction
Case Study 1: Le Chatelier’s principle is also known as the equilibrium law, used to predict the effect of change on a system at chemical equilibrium. This principle states that equilibrium adjusts the forward and backward reactions in such a way as to accept the change affecting the equilibrium condition. When factor-like concentration, pressure, temperature, and inert gas that affect equilibrium are changed, the equilibrium will shift in that direction where the effects caused by these changes are nullified. This principle is also used to manipulate reversible reactions in order to obtain suitable outcomes.
Q16.Which one of the following conditions will favour the maximum formation of the product in the reaction?
(i)
(a) Low temperature and high pressure
(b) Low temperature and low pressure
(c) High temperature and high pressure
(d) High temperature and low pressure
(ii)For the reversible reaction,
The equilibrium shifts in forwarding direction
(a) by increasing the concentration of NH3(g)
(b) by decreasing the pressure
(c) by decreasing the concentrations of N2(g) and H2(g)
(d) by increasing pressure and decreasing temperature.
(iii)Favourable conditions for manufacture of ammonia by the reaction
(b) low temperature, high pressure and catalyst
(c) high temperature, low pressure and catalyst
(d) high temperature, high pressure and catalyst
Q.17. Justify that the following reactions are redox reactions:
(a) CuO (s) + H2(g) —–> Cu(s) + H20(g)
(b) Fe2O3 (s) + 3CO(g) —-> 2Fe(s) + 3CO2(g)
(c) 4BCl3(g) +3LiAlH4(s) ——> 2B2H6(g) + 3LiCl(s) + 3AlCl3(s)
SECTION -D (4M EACH)
Q.18.Write formulas for the following compounds:
(a) Mercury (II) chloride,
(b) Nickel (II) sulphate,
(c) Tin (IV) oxide,
(d) Thallium (1) Sulphate
Q.19.What is the effect of:
(i) addition of H2
(ii) addition of CH3OH
(iii) removal of CO
(iv) removal of CH3OH
SECTION -E (5 M)
Q.20. At 473 K, the equilibrium constant Kc for the decomposition of phosphorus pentachloride (PCl5) is 8.3 x 10-3 . if decomposition proceeds as:
(a) Write an expression for Kc for the reaction
(b) What is the value of Kc for the reverse reaction at the same temperature.
(c) What would be the effect on Kc
if
(i) More of PCl5is added
(ii) Temperature is increased.