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Questions and Answers
In which scenario does a change in oxidation number occur?
Which actinoid element does not commonly exhibit variable oxidation states?
Ferrates (VI) are formed in alkaline media but decompose readily to:
Which member of the first transition series does not commonly display variable oxidation states?
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Given pH values x and y for Cr2O7^2- and CrO4^2-, respectively, what are the possible pH values?
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When an excess of KCN is added to a solution of CuSO4, what is the final product obtained?
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What is the oxidation number of Pt atom in [Pt(Py)4] part of the complex?
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Which pair of species has the same number of unpaired electrons?
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Which hybrid state is associated with low spin octahedral complex?
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How does hydrazine act as a ligand?
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Arrange the following complex entities in increasing order of electrical conductivity in aqueous solution.
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What is the oxidation number of Pt atom in the latter part of the compound [Pt(Py)4] [PtCl4]?
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If the volume of a container is reduced to 1/4 of the initial volume, how many times will the rate of the reaction be compared to the initial rate, according to the given information?
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In a reaction A + B products, if the order of A is 1 and the order of B is 1/2, by what factor will the rate increase when concentrations of both A and B are increased four times?
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In a first-order reaction, if the concentration of the reactant decreases from 1.0 M to 0.25 M in 20 minutes, what is the rate constant of the reaction?
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If 99% of a first-order reaction was completed in 32 minutes, how long will it take for 99.9% of the reaction to complete?
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If doubling the initial concentration of a reactant also doubles the half-life (t½) of the reaction, what is the order of the reaction?
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In a first-order reaction, if the concentration of a reactant decreases from 1.0 M to 0.25 M in 20 minutes, how does this affect the rate constant?
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In which of the following equilibrium reactions would the equilibrium shift to the right side if the total pressure is decreased?
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What is the pH of a solution containing 2 × 10^−3 moles of OH− ions in a 2-liter solution?
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In the expression α = 0.1 × C−1, where C is the concentration of the acid, what is the pH of the solution?
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Which set of solutions shows the common ion effect?
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If H2S is a weak acid and ionizes into 2H+ and S^–2, what can be inferred about its dissociation?
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Which equilibrium reaction represents a reaction that can shift to the right side when temperature is decreased?
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What is the consequence of attempting more than 10 questions in a candidate's exam?
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When NH4Cl is added to a solution of NH4OH, what happens to the concentrations of OH- and NH4+ ions?
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Which ion does not give the borax bead test?
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In a reaction involving AgCl and Na3AsO3, what is the observation?
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What is formed when HNO3 is added to sodium ferrocyanide?
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Which pair(s) of ions form precipitates upon passing H2S gas in the presence of dilute HCl?
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Study Notes
Chemical Reactions
- Rate of reaction: If the volume of a container is reduced to 1/4 of its initial volume, the rate of reaction will increase by a factor of 8.
- Order of reaction: The order of a reaction is 1 for A and 1/2 for B, so when the concentration of both A and B are increased four times, the rate will increase by a factor of 8.
First-Order Reactions
- Concentration of reactant: If the concentration of a reactant is decreased from 1.0 M to 0.25 M in 20 minutes, the rate constant of the reaction is 0.6931 min-1.
- Time for completion: 99% of a first-order reaction is completed in 32 minutes, so 99.9% of the reaction will be completed in approximately 50 minutes.
Order of Reaction
- Effect of concentration on rate: If doubling the initial concentration of a reactant doubles the half-life of the reaction, then the order of the reaction is 0.
Chemistry of Transition Elements
- Ionization: Fe3+ has a magnetic moment of 3.9 B.M.
- Oxidation states: Actinoids do not show a common and variable oxidation state.
Complexes
- Ferrates (VI) are formed in alkaline media but readily decompose to Fe3O4 + O2.
- pH values: Cr2O72- + pH = x, CrO42- + pH = y, where x and y are pH values.
Coordination Compounds
- Oxidation number: In [Pt(Py)4] [PtCl4], the oxidation number of Pt is +2 and +4 respectively.
- Unpaired electrons: [CoF6]3- and [FeF6]3- have the same number of unpaired electrons.
Electrolytic Conductivity
- Increasing order of electrical conductivity: [Co(NH3)4Cl2]Cl < K2[PtCl6] < [Cr(NH3)6]Cl3 < [Pt(NH3)6]Cl4.
Chemical Equilibrium
- Shift in equilibrium: If the total pressure is decreased, the equilibrium would shift to the right side in the reaction N2(g) + 3H2(g) 2NH3(g).
pH and pOH
- pH calculation: If a solution has 2 × 10-3 moles of OH- ions in 2 liters of solution, the pH of the solution is 11.
- Degree of dissociation: The degree of dissociation of acetic acid is given by the expression α = 0.1 × C-1, where C is the concentration of the acid.
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Description
Test your knowledge on oxidation numbers in chemistry with this quiz. Identify cases where there is a change in oxidation number and common/variable oxidation states of actinoids. Determine which compounds exhibit variable oxidation states.
