Chemistry

The hydrogen atom has only one electron, so mutual repulsion between electrons is absent. However, in multielectron atoms mutual repulsion between the electrons is significant. How does this affect the energy of an electron in the orbitals of the same principal quantum number in multielectron atoms?

Hydrogen atom has only one electron, so the mutual repulsion between the electrons is non-existent. However, in multielectron atoms the interaction between electrons is important. This is because,...

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Which of the following is responsible to rule out the existence of definite paths or trajectories of electrons? (i) Pauli’s exclusion principle. (ii) Heisenberg’s uncertainty principle. (iii) Hund’s rule of maximum multiplicity. (iv) Aufbau principle.

Correct Answer: (ii) Heisenberg’s uncertainty principle. Explanation: The Heisenberg's uncertainty principle states that it is impossible to know the exact position and speed of an object...

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A box contains some identical red coloured balls, labelled as A, each weighing 2 grams. Another box contains identical blue coloured balls, labelled as B, each weighing 5 grams. Consider the combinations AB, AB2, A2B and A2B3 and show that the law of multiple proportions is applicable.

AB ab2 A,B A2B3 Mass of A (in g) 2 2 4 415 Mass of B (in g) 5 10 5   According to the law of multiple proportions, Masses of B combines with a constant mass of A are 10g, 20g, 5g, 15g Simple...

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Assertion (A): Significant figures for 0.200 is 3 whereas for 200 it is 1. Reason (R): Zero at the end or right of a number are significantly provided they are not on the right side of the decimal point. (i) Both A and R are true and R is the correct explanation of A. (ii) Both A and R are true but R is not a correct explanation of A. (iii) A is true but R is false. (iv) Both A and R are false.

Correct Answer: (iii) A is true but R is false Explanation: Zero at the end of a number without the decimal point is not significantly based on the rate of accuracy.

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The reactant which is entirely consumed in the reaction is known as limiting reagent. In the reaction 2A + 4B → 3C + 4D, when 5 moles of A react with 6 moles of B, then (i) which is the limiting reagent? (ii) calculate the amount of C formed?

(i) The reactant B is the the limiting reagent. (ii) Calculation: Let us consider that the reactant B got completely consumed as it is the limiting reagent. 4 mol of B gives 3 mol of C 6 mol of B...

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Two students performed the same experiment separately and each one of them recorded two readings of mass which are given below. The correct reading of mass is 3.0 g. Based on given data, mark the correct option out of the following statements. Student Readings

(i) (ii) A 3.01 2.99 B 3.05 2.95 (i) Results of both the students are neither accurate nor precise. (ii) Results of student A are both precise and accurate. (iii) Results of student B are neither...

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The strain volume work for an ideal gas can be determined by utilizing the articulation w= ʃPexdv. The work can likewise be determined from the pV–a plot by utilizing the region under the bend inside as far as possible. At the point when an ideal gas is compacted (a) reversibly or (b) irreversibly from volume Vi to Vf. pick the right alternative.

    \[\begin{array}{*{35}{l}}    \left( I \right)\text{ }w\text{ }\left( reversible \right)\text{ }=\text{ }w\text{ }\left( irreversible \right)  \\    ~  \\    \left( ii \right)\text{ }w\text{ }\left( reversible \right)\text{ }<\text{ }w\text{ }\left( irreversible \right)  \\    ~  \\    \left( iii \right)\text{ }w\text{ }\left( reversible \right)\text{ }>\text{ }w\text{ }\left( irreversible \right)  \\    ~  \\    \left( iv \right)\text{ }w\text{ }\left( reversible \right)\text{ }=\text{ }w\text{ }\left( irreversible \right)\text{ }+\text{ }pex.V  \\ \end{array}\]

Arrangement:   Alternative (ii) is the appropriate response. w (reversible) < w (irreversible) Region under the bend is more noteworthy in irreversible pressure than that of reversible...

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An ideal gas is permitted to grow against a consistent strain of 2 bar from 10 L to 50 L in one stage. Compute the measure of work done by the gas. In the event that a similar development were done reversibly, will the work is done be higher or lower than the prior case?

    \[\left( Considering\text{ }that\text{ }1\text{ }L\text{ }bar\text{ }=\text{ }100J \right)\]

solution:   \[\begin{array}{*{35}{l}} Measure\text{ }of\text{ }work\text{ }done\text{ }=\text{ }-\text{ }pext\text{ }V  \\ ~  \\ =\text{ }\text{ }2\text{ }bar\text{ }\times \text{ }\left(...

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The net enthalpy change of a response is the measure of energy needed to break every one of the bonds in reactant atoms less the measure of energy needed to shape every one of the bonds in the item particles. What will be the enthalpy change for the accompanying response?

    \[H2\left( g \right)\text{ }+\text{ }Br2\left( g \right)\text{ }\to \text{ }2HBr\left( g \right)\]

Considering that Bond energy of H2, Br2 and HBr is 435 kJ mol–1, 192 kJ mol–1 and 368 kJ mol–1 separately.

solution:   For the response   \[H2\left( g \right)\text{ }+\text{ }Br2\left( g \right)\text{ }\to 2HBr\left( g \right)\] \[\begin{array}{*{35}{l}} Enthalpy\text{ }change  \\ ~  \\ =\text{...

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. Enthalpy is a broad property. As a rule, if the enthalpy of a general response A→B along one course is Δr H and Δr H1, ΔrH2, ΔrH3 … .. address enthalpies of middle responses prompting item B. What will be the connection between ΔrH for generally speaking response and ΔrH1, ΔrH2… .. and so forth for moderate responses.

solution:   For the response, A→B the development of B goes through a few middle of the road responses with various enthalpy esteems Δr H1, ΔrH2, ΔrH3… .., and the general enthalpy change is Δr...

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18.0 g of water totally vapourises at 100°C and 1 bar pressure and the enthalpy change in the process is 40.79 kJ mol–1. What will be the enthalpy change for vapourising two moles of water under similar conditions? What is the standard enthalpy of vapourisation for water?

solution:   Enthalpy change of vapourisation for \[1\text{ }mole\text{ }=\text{ }40.79\text{ }kJ\text{ }mol1\] enthalpy change of vapourisation for \[2\text{ }moles\text{ }of\text{ }water\text{...

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. Think about the accompanying response among zinc and oxygen and pick the right alternatives out of the choices given underneath :

    \[2\text{ }Zn\text{ }\left( s \right)\text{ }+\text{ }O2\text{ }\left( g \right)\text{ }\to \text{ }2\text{ }ZnO\text{ }\left( s \right)\text{ };\text{ }H\text{ }=\text{ }\text{ }693.8\text{ }kJ\text{ }mol1\]

(i) The enthalpy of two moles of ZnO is not exactly the absolute enthalpy of two moles of Zn and one mole of oxygen by 693.8 kJ. (ii) The enthalpy of two moles of ZnO is more than the absolute enthalpy of two moles of Zn and one mole of oxygen by 693.8 kJ. (iii) 693.8 kJ mol–1 energy is advanced in the response. (iv) 693.8 kJ mol–1 energy is caught up in the response.

solution:   Choice (I) and (iii) are the appropriate responses

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. For an optimal gas, crafted by reversible extension under isothermal condition can be determined by utilizing the articulation

    \[w\text{ }=\text{ }\text{ }nRT\text{ }ln\text{ }Vf/Vi\]

An example containing 1.0 mol of an ideal gas is extended isothermally and reversibly to multiple times of its unique volume, in two separate tests. The extension is completed at 300 K and 600 K separately. Pick the right alternative. (I) Work done at 600 K is multiple times the work done at 300 K. (ii) Work done at 300 K is double the work done at 600 K. (iii) Work done at 600 K is double the work done at 300 K. (iv) ∆U = 0 in the two cases.

solution:   Alternative (iii) and (iv) are the appropriate responses. work done at 600 K is double the work done at 300 K. Since each case includes isothermal extension of an optimal gas, there...

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The immediacy implies, having the capacity to continue without the help of an outer organization. The cycles which happen immediately are (I) stream of warmth from colder to hotter body. (ii) gas in a compartment contracting into one corner. (iii) gas extending to fill the accessible volume. (iv) consuming carbon in oxygen to give carbon dioxide.

solution:   Alternative (iii) and (iv) are the appropriate responses. Gas grows or diffuses in accessible space suddenly, e.g., spillage of cooking gas gives smell of ethyl mercaptan...

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. Thermodynamics essentially manages (I) interrelation of different types of energy and their change from one structure to another. (ii) energy changes in the cycles which rely just upon starting and last conditions of the minute frameworks containing a couple of particles. (iii) how and at what rate these energy changes are done. (iv) the framework in harmony state or moving from one balance state to another harmony state.

solution:   Alternative (I) and (iv) are the appropriate responses. Thermodynamics manages interrelation of different types of energy and their change into one another. It additionally manages...

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. Which of coming up next isn’t right? (I) ∆G is zero for a reversible response (ii) ∆G is positive for an unconstrained response (iii) ∆G is negative for an unconstrained response (iv) ∆G is positive for a non-unconstrained response

solution:   Alternative (ii) is the appropriate response.   ∆G gives a basis for suddenness at consistent strain and temperature.   (I) If ∆G is negative (< 0). the cycle is...

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The entropy change can be determined by utilizing the articulation

    \[S\text{ }=\text{ }qrev/T\]

At the point when water freezes in a glass container, pick the right assertion among the accompanying : (I) ∆S (framework) diminishes however ∆S (environmental factors) stays as before. (ii) ∆S (framework) increments yet ∆S (environmental elements) diminishes. (iii) ∆S (framework) diminishes yet ∆S (environmental elements) increments. (iv) ∆S (framework) diminishes and ∆S (environmental factors) likewise diminishes.

solution:   Alternative (iii) is the appropriate response. During the method involved with freezing energy is released,which is consumed by the environmental factors. Therefore,the entropy off...

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Hydrogen bonds are formed in many compounds e.g., H2O, HF, NH3. The boiling point of such compounds depends to a large extent on the strength of hydrogen bond and the number of hydrogen bonds. The correct decreasing order of the boiling points of the above compounds is : (i) HF > H2O > NH3 (ii) H2O > HF > NH3 (iii) NH3 > HF > H2O (iv) NH3 > H2O > HF

Solution: Option (ii) is the answer.

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In an adiabatic interaction, no exchange of warmth happens among framework and environmental elements. Pick the right choice with the expectation of complimentary extension of an optimal gas under adiabatic condition from the accompanying.

    \[\begin{array}{*{35}{l}}    \left( I \right)\text{ }q\text{ }=\text{ }0,\text{ }T\text{ }\ne \text{ }0,\text{ }w\text{ }=\text{ }0  \\    ~  \\    \left( ii \right)\text{ }q\text{ }\ne \text{ }0,\text{ }T\text{ }=\text{ }0,\text{ }w\text{ }=\text{ }0  \\    ~  \\    \left( iii \right)\text{ }q\text{ }=\text{ }0,\text{ }T\text{ }=\text{ }0,\text{ }w\text{ }=\text{ }0  \\    ~  \\    \left( iv \right)\text{ }q\text{ }=\text{ }0,\text{ }T\text{ }<\text{ }0,\text{ }w\text{ }\ne \text{ }0  \\ \end{array}\]

solution:   Choice (iii) is the appropriate response. With the expectation of complimentary extension w = 0 For adiabatic cycle q = 0 From first law of thermodynamics,  ...

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Which of the accompanying assertions is right? (I) The presence of responding species in a covered measuring utencil is an illustration of an open framework. (ii) There is a trade of energy just as a matter between the framework also, the environmental elements in a shut framework. (iii) The presence of reactants in a shut vessel made down of copper is an illustration of a shut framework. (iv) The presence of reactants in a canteen jar or some other shut protected vessel is an illustration of a shut framework.

solution: Alternative (iii) is the appropriate response. For a shut vessel made down of copper, regardless of can be traded between the framework and the environmental elements however energy trade...

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Thermodynamics isn’t worried about______. (I) energy changes associated with a substance response. (ii) the degree to which a substance response continues. (iii) the rate at which a response continues. (iv) the practicality of a synthetic response.

solution: Choice (iii) is the appropriate response. This is because Thermodynamics informs us concerning the practicality, energy changes and degree of compound response. It doesn't informs us...

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Isostructural species are those which have the same shape and hybridisation. Among the given species identify the isostructural pairs. (i) [NF3 and BF3] (ii) [BF4- and NH4+] (iii) [BCl3 and BrCl3] (iv) [NH3 and NO3-]

From a structural standpoint, we can see that, NF3 is pyramidal whereas BF3 is planar triangular. BF4- and NH4+ ions are tetrahedral in structure. BCl3 is triangular planar and BrCl3 is...

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