Chemistry Discussion Test-5 2026

[00:00:01]Welcome to NGcon online academy. This lecture I'm send test number five key discussion for the reaction 2 a + b forms 2 c. The concentration of a changes from 8 to 2 in 1 minute. So what is the rate of reaction?

[00:00:18]So reactant a rate of reaction the change in concentration of 8 divided by 2 into time.

[00:00:29]So a concentration change 8 say 2 and time 1 minute which is equal to 60 seconds. So here 6 / 120. So 6 / 12 is 0.5. 6 / 120 is 0.05.

[00:00:56]So P is the correct option.

[00:01:00]Shape of a subshell is determined by subshell shape quantum number quantum number.

[00:01:11]A molecule having a central atom with three electron pairs. So molecule elects 1 2 and three pairs angular geometry under which set of experimental conditions does a real gas behave like ideal gas? So real gases ideal gases behave when pressure is low and temperature is high or ideal behavior deviate when pressure is high and temperature is low. So real gases behave like ideal at low pressure and high temperature. So A is the correct option.

[00:02:00]Change in which of the below mentioned factor does not lead to change in density of a liquid. So that is pressure liquids are incompressible.

[00:02:13]So density remains unaffected.

[00:02:22]Using which parameter can the state of equilibrium be recognized? Color or density of reaction mixture, pressure of reactants or products, constancy of concentration. So properties different type reactions equilibrium recognize.

[00:02:39]So this has been taken from textbook. So all of these is the correct option for the three parameters involved in first law of thermodynamics. Equation E is equal to Q + W. Which statement holds true? So this equation E, Q or W involved to which statement is correct?

[00:03:00]Work done by the system is taken as negative. This is correct. E, Q and W have same units. Yes. E or Q plus W units should be same. This is the equation of law of conservation of energy. This is also correct. So all of these would be correct. Which of the following reactions can be classified as an oxidation reaction. So here electrons are being gained. So this is reduction.

[00:03:27]Here also electron is being gained. So this is also reduction. If we see here, here nitrogen is minus3. It moves to zero. So it is being oxidized. If we see its oxidation state and if we see other side NH3 is losing hydrogen. So loss of hydrogen is also oxidation. So C is correct option. In order to perform stometric calculations but conditions must be met. So in order to perform stometric calculation equation must be balanced. There should be no side reaction occurring. Mass should be conserved on both sides. So all of these conditions are correct.

[00:04:04]If two electrons are placed in 2p subshell. So we have 2p subshell. In 2p subshell we have three sub subshells.

[00:04:14]Now we have placed two electrons in such a way that their spin quantum number is different. So we have placed them like this. One has spin plus half and the other one is having spin minus half. So which rule of electronic configuration is violated? So we have basically violated rule because if we are to place two electrons in 2p subshell. So one should go to px and one should go to py their spin quantum number should be same. Their magnetic quantum number should be different among CH43 CH2 and CL4. Which pair of molecules has zero net dipole moment? So, CH4 and CL4 these both are tetrahedral molecules with zero dipole moment because all the dipoles are cancelled due to the symmetry of molecule.

[00:05:10]If the temperature of a gas is doubled, so doubling the temperature makes the volume go double and pressure is increased by eight times. So if we increase the pressure eight times volume becomes 8 times less. So overall how the volume is affected. Volume is doubled by temperature and volume is decreased eight times by pressure. So overall the effect on volume is that it becomes 1/4.

[00:05:34]So it decreases to 1/4 of its original value.

[00:05:40]50 cm cube of acetone is mixed with 25 cm of chloroform liquid. So the new volume of the mixture is normally if you mix two liquids 50 + 25 the volume should be 75 but acetone has dipole dipole forces. Chloroform has dipole dipole forces. If we mix them together they form hydrogen bond with each other.

[00:06:04]So after mixing their forces become strong. So their volume becomes less due to stronger forces. So the volume is going to be less than 75 cm cube.

[00:06:16]For the reversible reaction, H2 plus I2 forms 2 HI. One mole of each H2 and I2 are taken initially. At a certain stage of reaction, the concentration of HI is found to be 1 mole per decime cube. But is true about the reaction at this stage if the value of its KC is 40. So now for this reaction, we have taken 1 mole of H2 and I2. So we write here H2 plus I2 gives off 2 HI. Initially we have taken one mole of both of them and at a certain stage of reaction the concentration of HI is found to be 1 mole. So the concentration of HI is 1 mole. So at equilibrium we can write 2X for HI and 1 - X for H2 and 1 - X for I2. So if 2X is equal to 1, X is going to be 0.5.

[00:07:08]So the concentration of H2 and I2 at equilibrium would be 1 - X any 1 - 0.5 it is 0.5. So now we calculate the QC at this stage. At this stage the QC would be HI² divided by H2 into I2.

[00:07:27]So the concentration at R time of measurement is 1 for HI and 0.5 for both H2 and I2. So it becomes 1 / 0.25 and QC is 4. So now QC is lesser than R KC. So if QC is lesser than the KC, a reaction will move forward in order to achieve equilibrium. Among the given processes, the one that is not exothermic is. So the one that is not exothermic is the D option. This has been taken from your textbook examples.

[00:08:04]When a zinc electrode dipped in 1 M zinc solution is coupled with SH at standard conditions, the voltmeter reads. So now we have created a zinc half cell and we couple it with standard hydrogen electrode. So on voltmeter we get the oxitation potential of zinc which is equal to 0.76 volt.

[00:08:27]mass of CO2 that is produced by decomposing 25 g of calcium carbonate under heat is. So now let's construct the balanced equation. Now we have given mass of Ca3 25 and its molar mass is 100. So the moles are 0.25.

[00:08:44]Now according to balanced equation one calcium carbonate forms 1 CO2. So 0.25 calcium carbonate form.25 CO2.

[00:08:54]So now we have to calculate the mass produced. So mass produced is equal to moles of CO2 produced multiply by molar mass of CO2. So we get 11 g of carbon dioxide.

[00:09:07]According to the off principle which of the following subshell filling sequences is incorrect. So we see the first sequence we have 4s and then 4 p. This is wrong. We know from transition elements that after 4s the element uh orbital that is filled is 3d and after then we have got 4 p. So this is the correct option. Which statement regarding the valence bond theory is correct? Carbon under goes excitation of electrons before forming CH4. This is correct. In the ground state, carbon has two unpaired electrons. So it can form only two bonds. But it excites its electron to p orbital to make four unpaired electrons so that it can form four bonds. Nitrogen forms NH3 by using pure unhybridized p orbitals with a bond angle of 90°. This is wrong. NH3 is a hybridized molecule which has sp3 hybridization in the nitrogen atom. 2s2s is stronger than 2p2p overlap. This is also wrong because the strength of overlap is 2 p 2p followed by 2 s 2p followed by 2 s 2s. So a is the correct option.

[00:10:21]A gas is taken at 25° centigrade temperature. Its volume is doubled at which temperature? So the gas is at 25.

[00:10:30]We first convert it into Kelvin. So 25 + 273 is equal to 298 Kelvin. Now its volume is doubled when temperature in centigrade is not doubled but the temperature in Kelvin is doubled. So the volume is going to double at 596 Kelvin. So 596 is not here in options.

[00:10:55]So we convert 596 Kelvin into centigrade by subtracting 273 from this temperature. So we get 323° centigrade.

[00:11:05]So the volume doubles at 323° centigrade. Rate of evaporation is least for which of the following liquids? So let's see their boiling points. This is almost 46. This is 76. This is 80. And this is 78. So this has got the highest boiling point. So the strongest IM forces. So its rate of evaporation is going to be least.

[00:11:30]If Ksp of a salt at 25° centigrade is lesser than the ionic product at 40, then so it means that Ksp is lesser than ionic product at 40. So if we cool down the solution, if we bring solution from 40° to 25°, so ionic product is going to equalize the Ksp. For that case, the precipitation is going to occur. So A is the correct option.

[00:12:00]Calculate the work done when a volume of a vessel changes from 15 to 20 under 2 atm pressure. So work done is equal to pressure into change in volume.

[00:12:11]So pressure is basically 2 atm. So we convert 2 atm into newton per meter squared. So we multiply to with 101 325.

[00:12:24]The change in volume is 5 DC m cube which when we convert into m cube would be 5 /,000.

[00:12:35]So now cancelelling it 2 into 5 is equal to 10.

[00:12:40]10 divided by 1,000 is equal to 1 divided by 100. So now we are left with 101325 by 100. So we have got 1013.25.

[00:12:53]So C is the correct option.

[00:12:56]Which of the following compounds is not a strong electrolyte? So these two are salts of sodium which are always strong electrolytes. This is sulfuric acid which is a strong acid. So obviously a strong electrolyte. Ammonium hydroxide is a weak base and therefore a weak electrolyte. Number of molecules is greatest in which of the following? 4 g of helium has 4 / 4 1 mole and it has 1 into a number of molecules. 49 g H2SO4 has 0.5 moles. So it has 0.5 into a number of molecules. 90 g of water has 5 moles. So it has 5 into a number of molecules. 22 g carbon dioxide has 0.5 into avocados number of molecules. So the number of molecules is greatest in 90 g of water.

[00:13:52]Canal rays is a specific name used for which of the following rays? So canal rays are a common name used for the positive rays.

[00:14:01]uh the difference between calculating an actual bond energy is V in the case of so we have HF at one extreme and HI at other extreme. Now we calculate bond energy for HF and for HI both but original bond energy is greater than our calculation because of the electro negativity difference between the two bonded atoms. So this difference is highest in HF because in HF the electro negativity difference is greater. So the actual bond energy is quite high as compared to our calculation. But in HI the actual bond energy is not much high compared to our calculation because the electro negativity difference is not so much pronounced in the case of HI. So D is the correct option.

[00:14:50]VT ratio of a certain gas taken at 25 according to Charles law is 2. So now if the temperature is increased to 27 the volume of the gas would be. So temperature is 27. We have to convert this temperature into Kelvin. So the Kelvin temperature is 300 kel for 27° centigrade. So volume divided by 300 is equal to 2. So volume is going to 2 * 300 is equal to 600. So B is the correct option.

[00:15:25]And X is passing through. So now we have a cubic crystal like this. Now we have Xing axis passing through mid of right and left face. So these are right and left faces and we have axis passing through here. So this is a tetra axis because this is the face that is moving on this axis and this face has four equal sides. So it is going to repeat its faces four times. So this is a tetrate axis.

[00:15:56]An acidic buffer is generated by mixing which of the following 1 mole HCl and.5 mole NaOH. So.5 mo Na O reacts with.5 moles of HCl and give us.5 moles of N A and we are left with.5 moles of HCl. So this is a strong acid. It does not form buffer. 1 mole formic acid 1 mole NaOH they react completely to form the salt. So there is no buffer going to be formed.

[00:16:28]1 mole CH3 C.

[00:16:31]So 1 mole CH3 CO and.5 moles NaOH.

[00:16:36]Now.5 moles NaOH reacts with.5 mo CH3 CO and we are getting.5 moles of sodium acetate. Along with that.5 moles of acetic acid are also left behind. So these two are a combination of weak acid and salt with a strong base. So this forms a buffer.

[00:17:00]Heat of sublimation equals to the sum of heats of vaporization and fusion of a substance according to. So heat of sublimation is equal to heat of fusion and heat of vaporization. This is according to what? So let's see we have solid into liquid into gas. So solid into gas is heat of sublimation.

[00:17:23]Solid into liquid is heat of fusion and liquid into gas is heat of vaporization.

[00:17:29]So this equals to sum of both of them.

[00:17:32]This is in accordance to Hess's law because Hess's law says if a process occurs directly or in a series of steps so the heat change in both the cases is going to be same two copper sulfate plus four potassium iodide in the equation given above. So copper is +2 here and iodine is minus1 here. iodine gets oxidized and copper gets reduced. So copper is the reducing agent. No, it is getting reduced so it is oxidizing agent. Ki is oxidizing agent. No. Ki is getting oxidized. So it is reducing agent. Copper plus2 is reduced. Yes.

[00:18:16]Copper plus2 is reduced into copper plus 1. This is correct statement.

[00:18:22]for the equation 3 H2 plus N2 forms 2 NH3. If 16 g of N2 is reacted with 2 g of H2. Okay.

[00:18:34]Now we have got 16 g of N2. So 16 divided by 28 are the moles is reacted by 2 g of H2. So we have 1 mole of hydrogen and 16 divided by 28 almost 0.6 6 moles of nitrogen.

[00:18:52]So which is going to be the limiting reagent? Now 3 moles of H2 react with 1 mole of N2. So 1 mole of H2 require 0.33 moles of N2. But we have greater moles of N2. Therefore H2 is the limiting reagent.

[00:19:11]In the lemon series of the hydrogen spectrum, uh it appears in which of the following regions of electromagnetic spectrum. So lemon series belongs to ultraviolet region of electromagnetic spectrum. Uh which of the orbitals does not have orientation in relation to x y or z-axis? So s orbital is spherically symmetrical. It does not have any orientation in relation to any of the axis. Density of same mass of a gas is maximum under which conditions of temperature and pressure. So density is maximum when volume is minimum. Volume is minimum when temperature is minimum and pressure is maximum. So we have to choose the option with maximum pressure and lowest temperature.

[00:19:54]So comparing this one and this one the temperature is same. Here the pressure is greater here the pressure is lesser. So cut this one.

[00:20:03]Now comparing this and this the pressure is same. Here temperature is low here temperature is greater. So cut this one.

[00:20:11]Now comparing this with this the pressure is larger here and temperature is lower here. So this one is the correct option.

[00:20:20]London dispersion forces are the only forces present in. Now London dispersion forces are normally present in all the molecules but they are only and only present in the non-polar. Only means that which of the following molecule has no other forces apart from London forces. So we have to choose the non-polar molecule here which is liquid bromine.

[00:20:42]For the reversible endothermic reaction, which of the following changes would favor the decomposition of PCL5? So, increasing the pressure, here the moles are two, here the moles are one. So, increasing the pressure reverses the reaction. So, this is wrong. Decreasing the temperature, the reaction is endothermic. Decreasing the temperature shifts the reaction backwards. So, this is also wrong. Adding the catalyst.

[00:21:06]Adding the catalyst does not affect the direction of reaction. Removal of Cl2. This is correct. Removing the product makes the reaction go towards the product or in the forward direction.

[00:21:19]So D is correct.

[00:21:21]For an exothermic reaction the sign of enthalpy change is so for exothermic reaction the sign of enthalpy change is negative.

[00:21:31]A chemist determines that a synthesis reaction typically operates at 75% heat.

[00:21:36]If the theoretical yield for a batch is calculated to be 12 g, what is the expected actual heat?

[00:21:43]Okay.

[00:21:46]So 75% is the yield. It is equal to actual yield divided by theoretical yield which is 12 g multiply by 100. So we get 75 into 12 divided by 100 is equal to actual sheet 25 3es are 75 25 4s are 100 4 3's are 12 so 3 and 3 9 g is going to be the actual heat.

[00:22:16]Isomorphs are crystals belonging to different compounds. These crystals differ in isomorphs are different in both physical as well as chemical properties. Sum of exponents to which the reactants in the rate equation are raised. So if we raise the reactants in a rate equation to exponents, the sum of these exponents is called the order of reaction.

[00:22:40]Since let energy cannot be measured directly, it is determined indirectly using. So let energy is calculated indirectly using the Hess's law and Hess's law has an application born he cycle which enables to calculate the latest energy. So B is the correct option. Crystal of Hgs has a unit cell belonging to. So this has been taken from textbook examples. Hgs belongs to robo system. Increasing the temperature of a reaction usually enhances the rate of reaction by which of the following mechanisms? So increasing the temperature enhances the rate of reaction by increasing kinetic energy.

[00:23:18]This is correct. Increasing collision frequency. This is correct. increasing ratio of reactant molecules possessing energy of activation. Yes, at low temperature few molecules have activation energy. At high temperature, the greater number of molecules possess activation energy. So, rate of reaction increases. D of D is the correct option all of these. Thank