Metal salts containing cations with high charge density (like Mg²⁺) undergo hydrolysis in water, producing hydronium ions (H₃O⁺) and making the solution acidic. For example, MgCl₂ dissociates into Mg²⁺ and Cl⁻, where Mg²⁺ reacts with water to form MgOH⁺ and H₃O⁺, demonstrating that cations with higher charges tend to produce acidic solutions through hydrolysis.
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PHYSICAL CHEM TEST-12 VIDEO SOLUTION FOR RE NEET-2026Added:
Goal Nations [Music] Leading Institute Hello Students Myself Riyaz Sir Senior Chemistry Faculty Goal Coaching Institute Once again I am going to discuss with you all questions of Physical Chemistry Test Series for REET 2026 Test 12 that was held on Fifth of June 2026 Okay let us start with the question C The question in fact the first question you are looking it is some what related to inorganic chemistry but can I discuss that the question says which of the following solution which of the following solution is acidic in water? Which salt solution is acidic in water? So you must know the answer. Whatever you are seeing, note it down in your copy. This magnesium salt that you are seeing is acidic in nature. What is the reason for that? The reason for this is that these magnesium ions will be related to water, the magnesium ion here Mg2+ will react with water.
It gives MgOH plus and also produces hydronium ion H3O+.
This is the cation which will give H+ ion i.e. hydronium ion. You know this way that the charge of magnesium is 2+ and the charge of OH is -1, if both are mixed then MgOH and one positive charge will remain and along with it H3O+ will be generated, so note this in your copy. It's a It's a question related to inorganic chemistry. But you should note it down. The cations that we see here have the property that they will interact with water and form MgOH+ and H3O+.
Third option: Okay, you guys can study and practice this a little from NCERT.
Next Question After Question No. 91 Question No. 94 The Solubility of AgCl This is a very important question. We are saying that this question came many times. The concept of this question has come many times in NEET exam and also in IT JE. And there is every probability of such a question coming.
See how it will be made. We will start with AgCl.
AgCl salt Ag+ Cl- its initial concentration C 0 C- S We have already discussed this type of question in the test series.
What substance is being mixed with this AgCl? That is magnesium chloride.
Now let us add magnesium chloride to it.
If you understand the concept.
MgCl2 Mg2+2Cl- concentration is given as 0.05 initially so this is zero this is finished 05 and this 2 * 05 is two moles so 2 * 05 common NaCl- minus here this is a theoretical question.
Not asking though. But in this solubility system, if magnesium chloride is added to the equilibrium system, the number of chlorine increases. Chlorine common ion and you know the quantity of the product will increase.
In which direction will the reaction go? Backward. This assertion can come in reasoning. is the common ion.
See, by adding magnesium chloride, chlorine ion became common chloride ion.
And if the quantity of the product increases then the reaction will move in the backward direction. Well, this has not been asked but we have told you that it will go in the backward direction and you know that the value of K will not change. Come to the KSPI mixture.
Ag + Many times before also, when you used to give the test series before the re-exam of NEET was cancelled. It came many times in that too. I remember in the video that many questions were of this type.
This question is very important. The value of k will not change. The value of K is 10 power -10 Ag + S, see there is Ag + S and Cl- S also and 2 * 05 S + 05 this is 05. 05 see let us write it down nicely. 2 * 05 when you multiply it it will come to 1 so s + 0.1 this much theory we know.
In comparison, the value of its comparison s is very weak.
We have told you many times that whenever we discuss this in the test, please tell us this.
Compared to this, it is very weak. Why does it become weak? Because see how less the power is -10, so the s that comes out from here is in very less quantity, so when we add s in point one, we will neglect it, so the answer is 10 power -10 = s * 0.1 If we write these two together then a quadratic equation will come which will get stuck, you should remember that in comparison to this, this s is always weak, so neglect it, the answer is 10 to the power -9 second option is the option to answer 94, okay move on to another question after question number 94 it is question number 97 assertion is reasoning type, read the following statement carefully assertion half life of first order reaction half life of a first order reaction is is independent of temperature.
This is wrong. It will not be independent. It is dependent. How to check it. Yes, live first order 693 / K and you know this K is temperature dependent, student. One of the Most Important and Sensitive Questions of Chemical Kinetics.
What are you saying? Just listen.
This is the formula for Half Life. The half-life depends on K.
And K is temperature dependent. If the temperature increases, the rate of reaction will increase. The rate constant will also increase. Now let us now come to the region on increasing temperature rate of reaction and rate constant increases.
Since the half-life time of any reaction decreases. This is absolutely correct. The first point which is written is assertion. Half Life First Order is independent on temperature. Wrong. This is temperature dependent. half life. The half- life is temperature dependent. The assertion was wrong. It is written in the region that if the temperature is increased then the rate of reaction will increase. The rate constant will decrease. Half Life: Look at the half life, if this increases then this decreases. The statement is correct. Means Assertion Wrong Reese Right. Third option is the answer. Three of 97.
These are all important questions. Note all this down in your copy. Correct? Move on. Another question. Let us see another question, question number 99, another tricky question, this has also come in NEET many times, you should understand one thing that in vacuum the external pressure is zero, the children of my batch know it, so I get all these points ticked in their copy with a colour pen, if the external pressure is zero then the work done will be zero because the formula of work done is - P external * change in volume when pressure is zero work done is zero then the work done is zero. Now isothermal as written in the question.
Isothermal means there is no external contact. Isothermal change in temperature zero. And you know change in temperature zero. So Delta E is also zero because internal energy is temperature dependent. Isothermal Change in Temperature Zero Internal Energy Zero. Now let us write the formula First Law of Thermodynamics delta = q + w See Student Work Done Zero delta is zero. So obviously this will also become zero. Everything will become zero. Therefore, whatever answer will be given to this, the answer will be two. Second option is the answer.
This type of concept came many times in NEET after question number 99, question number 103, so first of all we will write the formula e = e not -059 / n lg base 10q, do you know that you can make such a question even without touching the pen. How?
Please understand the trick.
See, as this factor increases, the value of E will decrease. This is a constant. Like this is 10, 2 out of 10 went at.
Listen carefully. If this is 10, let us assume it is an imaginary value and after calculating it, it comes out to be 2, then 2 out of 10 gives 8. If after calculating this, it comes out to be four, then it will be four out of 10, so it will be six. After calculation it came to eight. If eight out of 10 is lost then this becomes two. So the point we want to make is that if this factor which we have rounded off increases then obviously E will decrease. Just check it. So we will write the first part.
Zinc converted to Zn2+ We are writing the first reaction.
Write the reaction of Cu2+ converted to Cu. These two electrons are right here. There are two electrons here. This will be cut. The reaction will be Zinc Zn2+ Cu2+ + Cu, so when you remove Q, it is solid. This will become a forest. Zinc one copper one reaction quotient so the formula of q will be Zn2+ Zn2+ is 1 and divided by Cu2+ Cu2+ is also one so this will become one so E will be equal to E note. So math is mathematics, listen carefully here. If we take option two, students please look carefully. Please take this statement. Statement to Zn2+ and this Cu2+ then this will be 0.1 / 1 its value will be negative. That means it will increase.
This will increase. Its value will be negative. I understand maths this much. This is log 10 to the power -1. This factor is additive to E not.
So the question we are asking is whose E value will increase? So take a closer look. E2 This E2 will have a plus sign here. When you solve it and put it in this formula, a plus sign will appear here. If you take the second factor, this value will increase and the highest value will be of E2. of E2.
We can see this in the fourth option. Now why are you saying E1 after E2? Because this has become zero. It's over. This factor will end. If we take the first statement. This will end. E and E not equal. Why would the lowest of the low come from E3? Because in E3, Zn2 + 1 will be on top and 0.1 will be below, this will come to log 10 and log 10 to base 10 will become one. So here the lowest value will be the answer to this.
What's the trick? Such a question has already come in NEET.
If this factor comes negative. If you solve this factor.
The more it increases, the more it will decrease. If this decreases then this will increase. So this is the way to make it. The option will become four. I hope you understood this question.
Take move on after question number 103 it's question. We have already discussed this question two-three times in the test series.
Same question. Now I even remember the answers of some children.
See 1.5 for the trick to solve this.
Rate Law. The rate law will depend on the slow reaction.
Here's the slow reaction. r = k * a * bt is asking for the order, so many times we should tell that the children who study sincerely and watch videos know it, so just look at the main reaction, a should be in the form of a2 and b should be in the form of b2. Here a should be in the form of a or a2 this is a. That means it became unstable.
Listen to it once again. The rate law will depend on the slow reaction.
In slow reaction A to the power of one, B2 to the power of one. Now who is unstable in this? This is unstable. How did you find out from here?
Should be A2. is A. B Okay, B2 is there so B2 is there here as well.
Main reaction will tell who is stable?
Who is it? Unstable. B2 is, B2 is. It is stable. But it should be A2. This is unstable.
Now we have to remove the unstable. To remove A, we have to remove A and get A2.
Where do you see A2? Here. Two fast reactions have been given. This is also given and this is also given. So which one will we use? We will use this. Because let's assume equation one is equation one and this equation is equation three. If we use equation one, we will get A2. a2 is not here. We need A2. There is no A2 here. There are two fast reactions. This is also there, this is also there. We will use this fast reaction because we can see A2 in it. Now let us take the equilibrium constant in this.
Equation One Let's talk about this equation. k = a * a² / a2 We need a a = Look carefully students, root on * a2 also, we take it to the power of half.
From here we take out a. a² = k * a2 so a = * a2 a2 means a2 pe ^ 1/2. Now this equation a is your main equation. Now we will come back to the main equation. Let's return to equation a. So we will write r = k and we have got the substitute of a, in place of a we will write a2 power 1/2 and this b2 is next to it, let it be b2 to the power 1, so after removing a we will write root of a2 to the power 1/2 constant times constant, a new constant will come, take it k, the answer is a2 to the power 1/2 and b2 to the power one overall order 1.5 overall order 1.5 add one and 0.5 1.5, we have discussed this question many times.
The answer will be the first option. So option one of 110 move on to another question after question number 110 it's question number 111 you know this the first thing we will do is look at the theory, H2SO4 plus NaOH compound will form sodium sulphate and water will be formed. Just remember the theory.
If we take one equivalent.
This is also one equivalent.
Remember the theory. Energy produced is equal to - 57.1 kjoules. This theory should be in the minds of all you children. If one equivalent of acid is one equivalent of base then energy produces 57.1 Now we have to find the equivalent of both. Let's start.
Find the equivalent of sulphuric acid. First we will find the molarity. Molarity is given. Look at 0.5 of H2SO4.
Look carefully. Here's the molarity. Number of moles is not known. Molarity is equal to the number of moles divided by the volume in milliliters. The volume is 500 cm.
Divide by 1000.
500 * 1000 is the molarity formula to calculate the number of moles. Two times divisible 0.5 / 2 5 / 20 1/4 1/4 came out. Number of moles. And remember, those children who do not know will note it down in their copy. There is a formula for number of equivalents.
Number of moles * n factor. The number of equivalents is equal to the number of moles * n factor. So here we will find the equivalent.
Equivalent number of moles is 1/4 and n factor of H2SO4 is two. So this will be 0.5, so the mill equivalent of H2SO4 is 0.5, okay. Now we have to use NaOH.
NaOH number of moles of NaOH given in the question is 0.2 molarity sorry 0.2 number of moles is not known. N Volume this is also 500 * 1000, look carefully. First let us find the number of moles. So its number of moles will be 0.1, its N factor is one. N factor one of NaOH.
So the number of equivalents will be equal to the number of moles.
So its number of equivalents is 0.1 and its number of equivalents is 0.5. Now let us look at the theory.
This is 0.5 equivalent and this is 0.1 equivalent. Will make with limiting reagent. The ratio should be 1:1.
If this is 0.5 then this should also be 0.5.
But this is less, this is the limiting reagent. This will decide how much product will be produced.
The answer has come. The energy from one equivalent is 57.1, so from 0.1 equivalent, the answer will be 5.71. This is the answer. The fourth option is made from equivalents and limiting reagents. We discussed such questions many times in the class.
OK move on to another question after question number 111 next question 112 if for a certain reaction this type of question has also been repeated many times in NEET. The Value of DeltaS See, we know the formula of DeltaS.
DeltaS = DeltaH/T The enthalpy change is 50 kilojoules. Keep in mind it is kilojoules. Here's the mole per joule.
And the given temperature is 450 Kelvin so 0 cancels 5 * 9 = 45 5 * 10 = 50 1000 / 9 will come around 111.1 Just remember the formula for spontaneous deltag = deltaH - t this is the given equilibrium temperature.
So the theory is in the minds of all the children.
DeltaG will be negative. That's why it is spontaneous. This factor will increase. If you keep increasing this, DeltaG will become negative. So as T deltaS temperature increases, deltaG will become negative. So the only temperature given greater than 111 is option two. The answer to the second option 112 will be two.
Second option. Ok? Move on. Another question.
112 It's question number 113 is an empirical formula question. It should be made. Number of moles of carbon 24 / We will take this as 24 in round off figure.
This will come to 2 moles. Now you can take this in round off figures.
This is how questions are made for NEET.
This is how IIT toppers and NEET toppers are made.
Taking four on 4.07 will make that atomic number one. So this four mole. Take four on 4.07.
How do you want to make it?
Take chlorine 71 in the entrance exam and divide it by 35.5. You know that the number of moles has to be found out. First divide this by the atomic mass of two and the smallest mole among these three is two. Divide all of them by two.
You know the theory. The smallest value among these three is two. Divide this by two. This one is 4 / 2, this two is 2 / 2, this one C1H2 CL CH2Cl.
Fourth option is the answer. CH2Cl This is the answer. This is an easy question. Even otherwise, questions on empirical formula are easy in NEET. Let's move ahead.
After question number 113, this is a bit calculative. This will have to be solved.
We will first write the formula for activation energy.
Remember. 2.303 LG 10 K2/ K1 EA/ R T2 - T1 T1 * T2 2.3 Look carefully at the value.
What is the second rate constant given? This 2k is given and this is 1k, so 2k on top and this 1 and this log log 2 log 2 will come 2 / 1 2 / 1, pay attention to this answer, you need kilojoule, the value of r is 8.314, take 8.3 divided by 1000 because the value of r is 8.3 joule per Kelvin per mole, if you need it in kilojoule then we will do it 8.3 by 1000, then it will come in kilojoule, 8.3 / 1000, two temperatures are given. A temperature is given 310 - 300, know a little trick of how the calculation is done, you can do it yourself, if it goes up to 1000 then we will find out ea, the value of log 2 is 0.3, we will solve it, second option is the answer, you can do the rest of the calculations yourself, second option is the answer, ok move on to another question, after question number 115, after question number 115 it is question number 119, let's solve it.
Reaction of PCL5 It is Guess PCL3 + Cl2 Initial moles X is 0 and degree of dissociation is alpha. x - x alpha this will become x alpha this will become x alpha. Add all the moles and find the equilibrium. x out of x alpha broken. When you add them all together, x alpha + x alpha cancels out and becomes x + x alpha. Partial pressure is required.
Apply Dalton's law for PCl3. Partial pressure of PCL3 own value. Own moles X alpha total moles is the formula. Hope you guys understand? This total moles also take x + x alpha and * p. But look here, in the question, p is being raised to the power of -1.
Here * p and then p to the power -1, so this cancels out. This is over.
The answer will be x alpha x common.
1 + alpha x cancelled alpha / 1 + alpha alpha / 1 + alpha third option third option is the answer this is a tricky question we know its own mole by total mole total mole this much is required of pcl3 its own mole is x alpha / x + alpha total mole multiplied by p is total pressure and in the question it is saying that do P - 1 with this also, take this, if you do p - 1 then both get cancelled this much will be left this is the answer ok. It's all a question of the mind. After 119 such questions, children will get stuck on the day of NEET exam.
You people have to make it with patience. Now come, you know the formula for this. H+ ion or OH- ion = W is student. KW.
You know this formula because there are as many H+ ions as there are OH-. H+ ions * OH- is KW and H+ and OH are the same. So in place of HOH we will write H+ ion. H+ ion * H+ ion = KW Square of H+ ion = KW H+ ion is KW What better formula is ready than this H+ ion is KW Now we need log p - log base 10 The value of KW is given in the question 2.5 * 10 power -14 and this is the root so put 1/2. The rest is calculation. I will solve it with a little caution. There is a minus sign. Please take care. log 2.5 base 10 log a + - log 10 power -14 Although log 2 is written in the question, but how will we calculate log 2.5? log 2.5 Use your brain a little. The value of log2 is 0.3, student the value of log 4 is log we need log 2.5 sorry the value of log 3 is 0.48 log3 0.48 round a figure to 0.5 so the value of log 2.5 will be its middle value 0.4 see what we did listen carefully log2 0.3 log 3 0.5 approximate so how will log 2.5 be calculated the mid value of these two is 0 4 see the answer is 1/2 * log 2.5 the value of log 2.5 is 0.4 - 0.4 and this + 4 this is 14 we will solve this 13.6 / 2 when we will calculate PA see 0.4 is taken out of this 14 13.6 / 2 the answer is 6.8.
6.8 is the answer. In which option is it given? Given in the third option. Answer number three for 122. Ok? Move on to another question.
After question number 122.
It's question number 133. Maximum energy.
Hey, it will be made without touching the pin. Gives energy.
This is maximum energy. Keep in mind its formula is -n F not. It looks like it. The value of n to. Zn2+ two electrons from Zinc Cu2+ two electrons from Cu Value of N to Faraday constant 96500 coulomb E Note: The value given is 1.1 This answer will come in joule but in the option it says kilojoule - 2 Divide it by 1000 and you get 96.5 * 1.1 this comes in kilojoule. If you want to score quickly in NEET, make 96.5 into 100.
The answer has come. Second option is the answer. Second option is the answer. There is a minus sign.
Take this for 100 on a NEET day. 100 * 2 This answer is around 200. This is close to 200. This is how one makes it to NEET. This is how toppers make it. Do the calculations quickly. The weak children remain entangled in maths.
Last Question 134.
Ok? Let Us See the Solution.
Hydrogen electrode. Write the reaction first.
Remember this. If the potential is not given then the reduction potential has to be taken. Many times we tell this thing in class also. This gas and this is the neutral solution given in the question.
Neutral solution means pH seven. pH if intake. So H+ ion 10 to the power -7 and pressure if not given in the question, this is all theory. The teacher must be telling you. We make all the children in our batch take notes.
Given hydrogen pressure is 1 atm and pH ions are 10 at -7 q will first extract q.
Q is equal to partial pressure of hydrogen one divided by the square of H+ ion 10 raised to the power -7 of the whole square and this is 10 to the power 14. Apply the formula to find E. Cell potential E = E = -0.59 / 2 * LG Q Reaction quotient Q The value of E = zero is known to all children. We will round it to 6 so that this question can be solved quickly and this log 10 to the power 14 log 10 raised to the power 14 solve it 7 * 06 the answer that will come, this answer will be the first option, this is made the answer will come - 0.4 this is the answer I hope you all understood the solution carefully ok students ok best of luck for your examination
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