Recent questions in Physics

If the values of $\Delta H_f^{\circ}\: for\: CH_4(g), C_2H_6(g), CO_2(g)\: and \: H_2O(l)$ are respectively $-74.85, -84.68, -393.5 \: and\: -286\: kJ/mol,$ predict which is more efficient fuel?

asked Mar 19, 2014 by thanvigandhi_1

1 answer

Calculate the resonance energy of $N_2O$ from the following data: $\Delta H_f^{\circ}$ of $N_2O = 82 \: kJ/mol$ , Bond energies of $N≡N,\: N=N,\: O=O \: and\: N=O$ bonds are $946,\: 418,\: 498\: and\: 607\: kJ/mol$ respectively

asked Mar 19, 2014 by thanvigandhi_1

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A two terminal device is connected in a circuit and is found that it conducts when either forward biased or reverse biased and also operates both in AC and DC. The device is

asked Mar 19, 2014 by meena.p

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Which of the following statements is not true?

asked Mar 19, 2014 by meena.p

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Which of the following will cool quickly

asked Mar 19, 2014 by meena.p

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Which of the four substance has lowest specific heat

asked Mar 19, 2014 by meena.p

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Newton's law of cooling is a special case of

asked Mar 19, 2014 by meena.p

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Which of the following can be used to determine the velocity of sound in solids and gases

asked Mar 19, 2014 by meena.p

2 answers

In the experiment to find the speed of sound using resonance column if we replace the water with any other liquid the resonance position will

asked Mar 19, 2014 by meena.p

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In resonance apparatus we get?

asked Mar 19, 2014 by meena.p

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Sound wave can be

asked Mar 19, 2014 by meena.p

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A choke is used to

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Ultra violet mercury lamp is made of quartz and not glass because

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Accuracy of a potentio meter does not depends on

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A sensitive galvanometer is one which

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Which of the following instrument has largest resistance.

asked Mar 19, 2014 by meena.p

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In Newton's cooling experiment to reduce loss of heat the calorimeter should have .

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Coolant in radiations automobile must be

asked Mar 19, 2014 by meena.p

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Calculate $\Delta H_{C-H}$ from the following data: $\Delta H^{\circ}_{combustion}$ of ethane and propane are $-372$ and $-530\: kcal/mol$ respectively, $\Delta H_f^{\circ}$ of $CO_2(g)$ and $H_2O(l)$ are $-94$ and $-68\: kcal/mol,\: \Delta H^{\circ}$ for $C(graphite) \rightarrow C(g)\: is\: 172\: kcal \: and\: \Delta H_{H-H} \: is\: 104 \: kcal.$

asked Mar 19, 2014 by thanvigandhi_1

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This symbol represents

asked Mar 19, 2014 by meena.p

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Estimate the value of $\Delta S^{\circ}_{298}$ for the dissociation of calcium carbonate given that, $\Delta H^{\circ}_{298}$ for the reaction is $178\: kJ$ . The equilibrium pressure is one bar at $897^{\circ}C.(R = 8.314\: J/Kmol)$

asked Mar 19, 2014 by thanvigandhi_1

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In the stress - strain graph for a wire Breaking point, yield point and Elastic limit are represented by points

asked Mar 19, 2014 by meena.p

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Calculate the bond energy of $C-H$ bond in methane from the following data: $C(s) + 2H_2(g) \rightarrow CH_4(g);\: \: \: \Delta H = -74.8\: kJ$ $H_2(g)\rightarrow 2H(g);\Delta H = 435.4\: kJ$ $C(s) \rightarrow C(g);\Delta H = 718.4 \: kJ$

asked Mar 19, 2014 by thanvigandhi_1

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The output current versus time graph of a Diode as a rectifier The average value of output current is :

asked Mar 19, 2014 by meena.p

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Find the temperature as a function of radius r in case of a cylindrical shell whose inner surface temperature and outer surface temperature are $\theta_1$ and $\theta_2$ . The inner and outer radii of the cylindrical shell are $r_1$ and $r_2$ .

asked Mar 19, 2014 by thanvigandhi_1

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A solid ball of steel is heated to $200^{\circ}\;C$ and left to cool. Which of the curve will show cooling of the ball.

asked Mar 19, 2014 by meena.p

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Three different materials are studied by plotting the graph between temperature against time as shown. Which is best preferred as

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To find focal length of convex lens using $U-V$ method. the graph between u and v is

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Angle of minimum deviation $\delta _m$ in a Prism depends on

asked Mar 19, 2014 by meena.p

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Part of the galvanometer which has electrical resistance is

asked Mar 19, 2014 by meena.p

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The precaution to be taken during determination of young's modulus using Searl's apparatus 1) Micrometer screw should be rotated in same direction while taking reading. 2) Reading should be taken immediately after loading or unloading to the experimental wire 3) The load added should be with in elastic limit.

asked Mar 19, 2014 by meena.p

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In the experiment to find the refractive index of the material of prism. by minimum deviation method $D_m$ the minimum deviation is observed from the graph plotted in the experiment . The graph is plotted between

asked Mar 19, 2014 by meena.p

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To find the focal length of a convex mirror we use indirect method because ,

asked Mar 19, 2014 by meena.p

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In the experiment to find internal resistance of Daniel cell using potentiometer with E as Emt of the cell 'L' the balancing length of the potentiometer wire when potentiometer circuit is closed. (when no current flows through cell. When $R= 5 \Omega$ is introduced the new balancing length is l.) Then the internal resistance of the cell is

asked Mar 19, 2014 by meena.p

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The experiment to verify ohm's law and to find 3 different wires and the graph are plotted as shown.

asked Mar 18, 2014 by meena.p

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In the Meter Bridge experiment to determine the resistance of given wire the error occurred due to non uniformity of meter bridge wire can be reduced by

asked Mar 18, 2014 by meena.p

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In Searle's experiment to determine the young's modulus of a wire. The diameter of the given wire is measured by using

asked Mar 18, 2014 by meena.p

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In the experiment to plot the graph between square of amplitude and time of a simple pendulum and dissipation of energy , the oscillation occur in viscous medium like air. the energy versus time graph looks like

asked Mar 18, 2014 by meena.p

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A heat engine absorbs heat q1 from a source at temperature $T_1$ and heat $q_2$ from a source a temperature $T_2$ . Work done is found to be $J(q_1+q_2)$ . This is in accordance with

asked Mar 18, 2014 by thanvigandhi_1

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A reaction is non-spontaneous at the freezing point of water but is spontaneous at the boiling point of water, then

asked Mar 18, 2014 by thanvigandhi_1

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In an irreversible process taking place at constant $T$ and $p$ and in which only pressure-volume work is being done, the change in Gibbs free energy $(dG)$ and change in entropy $(dS)$ , satisfy the criteria

asked Mar 18, 2014 by thanvigandhi_1

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A copper wire of length L and cross sectional Area A is used and the corresponding current Vs voltage graph is drawn as shown.The slope of the curve becomes

asked Mar 18, 2014 by meena.p

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If the bond dissociation energies of $XY, X_2 \: and \: Y_2$ (all diatomic molecules) are in the ratio of 1:1:0.5 and $\Delta H_f$ for the formation of XY is -200 kJ/mol. The bond dissociation energy of $X_2$ will be

asked Mar 18, 2014 by thanvigandhi_1

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Consider the reaction $N_2 + 3H_2 \rightarrow 2NH_3$ carried out at constant temperature and pressure. If $\Delta H\: and\: \Delta U$ are the enthalpy and internal energy changes for the reaction, which of the following expressions is true?

asked Mar 18, 2014 by thanvigandhi_1

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A drop of water falling in air reaches the ground with terminal momentum P. Another drop of water of twice the radius reaches the ground with terminal velocity will have momentum.

asked Mar 18, 2014 by meena.p

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In resonance column experiment to determine the velocity of sound, $L$ person observes first resonance at $12\;cm$ . If she repeats the experiment on a very hot day her resonance column length would be

asked Mar 18, 2014 by meena.p

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The enthalpy changes for the following processes are listed below $Cl_2(g) = 2Cl(g),\: \: \: \: \: 242.3\: kJ/mol$ $I_2(g) = 2I(g), \: \: \: \: \: 151\: kJ/mol$ $ICl(g) = I(g) + Cl(g),\: \: \: 211.3 \: kJ/mol$ $I_2(s) = I_2(g),\: \: \: \: 62.76\: kJ/mol$ Given that the standard states for iodine and chlorine are $I_2(g)\: and \: Cl_2(g)$ , the standard enthalpy of formation of $ICl(g)$ is

asked Mar 18, 2014 by thanvigandhi_1

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An ideal gas is allowed to expand both reversibly and irreversibly in an isolated system If $T_i$ is the initial temperature and $T_f$ is the final temperature, which of the following statements is correct?

asked Mar 18, 2014 by thanvigandhi_1

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Potentiometer wire is of cross sectional area $8 \times 10^{-6}m^2$ and has resistivity $40 \times 10^{-8}$ . If $0.2$ amp current flows through it its potential gradient is

asked Mar 18, 2014 by meena.p

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The standard enthalpy of formation $(\Delta H_f^{\circ} )\: at\: 298\: K$ for methane, $CH_4(g),$ is -74.8 kJ/mol. The additional information required to determine the average energy for $C-H$ bond formation would be

asked Mar 18, 2014 by thanvigandhi_1

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