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We have to prepare a solution of 0.2M NAOH from the available 1M solution that is given to us how much volume of 1M NAOH is required to be taken which contains 0.2 moles of sodium hydroxide

Posted by Sonali Priya (Jul 23, 2017 10:58 a.m.) (Question ID: 6863)

• 1M solution of NaOH means that 1 litre of solution has 1 mole of NaOH.

We need 0.2 mole of NaOH.

Since 1 litre contains 1 mole NaOH , so 0.2 litre will contain 0.2 moles.

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Electronic configurstion of Re Rhenium (z=75).

Posted by Kriti Bhawsar (Jul 22, 2017 2:19 p.m.) (Question ID: 6830)

• {tex}1s^22s^22p^63s^23p^63d^{10}4s^24p^64d^{10}\\5s^25p^64f^{14}5d^56s^2{/tex}

Answered by Sahdev Sharma (Jul 22, 2017 2:44 p.m.)
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In what basis  chemical equation divided into two or more chemical equations in partial equation method of balanced equation?

Posted by Kriti Bhawsar (Jul 20, 2017 7:58 p.m.) (Question ID: 6794)

• Partial equation method:

Partial equation method is used for balancing complex chemical equations. There are chemical equation which involves many steps and reacting elements occur in more than one products in the product side. In such cases, balancing by Hit and Trial method is difficult. That is why partial equation method is used to balance such chemical equations.

In Partial equation method, equation is first divided into partial equation, which are simply probable steps that might occur in the chemical reaction. These probable steps are then balanced by hit and trail method and finally added. Following steps are applied in balancing chemical equation by partial equation method.

1. At first, different probable steps are written for the given chemical equation. These probable steps are simply the partial chemical equation which we can write for easily balancing the reactants and product. Note that the probable steps may or may not occur in real.
2. After breaking down the probable steps for the chemical equation, the partial equations are individually balanced by using Hit and Trial Method.
3. Such balanced partial equations are multiplied by suitable integer. This is done if required, so that the elements which are not formed in the product side of the overall chemical equation is canceled out.
4. Finally, the balanced partial equations are added to get the final overall balanced equation.

Lets’ illustrate some examples:

PbS + O3    →PbSO4 + O2

In the given reaction, the atom of Pb and S is balanced in both reactant and product side. But there is 3 atom of oxygen in reactant side and 6 oxygen atom in product side. So let’s balance this chemical equation by partial equation method.

• First let’s think the possible step for occurring of the given chemical reaction. There is lead sulphide reacting with ozone, it means ozone must be acting as oxidizing agent which liberates nascent oxygen. So the first step can be generation of nascent oxygen by decomposition of ozone molecule.

Step-1

O3  →O2 + [O]

This liberated nascent oxygen can react with PbS to give lead sulphate and oxygen as;

Step-2

PbS + [O] → PbSO4

This partial step is not balanced reaction. There is equal number of Pb and S atom, but no. of oxygen is one in reactant side but four in product side. So we can multiply nascent oxygen in reactant side by four.

PbS + 4[O] → PbSO4

If we make four nascent oxygen in second probale step, then we must also need to make it equal number of nascent oxygen liberated in step one. So we need to multiply step one with integer four

{ O3  →O2 + [O]    }    × 4

Now lets add both partial equation:

{ O3   →O2 + [O]    }  × 4

PbS + 4[O] → PbSO4

PbS  + 4O3   PbSO4 + 4O2

This is the balanced chemical equation.

Answered by Ashutosh Kumar (Jul 22, 2017 1:52 p.m.)
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What do you mean by hybridization of carbon

Posted by Abhishek Kumar (Jul 19, 2017 9:19 p.m.) (Question ID: 6776)

• hybridisation means the process of intermixing orbital with nearly same energy to get hybrid orbital with equal energy.

Posted by Durgesh Bishi (Jul 19, 2017 9:53 p.m.)
• Hybridization happens when atomic orbitals mix to form new atomic orbitals. The new orbitals have the same total electron capacity as the old ones.  The properties and energies of the new, hybridized orbitals are an 'average' of the original unhybridized orbitals.

Answered by Arun Soni (Jul 19, 2017 9:29 p.m.)
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who founded chemistry

Posted by Kanish Jarvis (Jul 19, 2017 8:04 p.m.) (Question ID: 6770)

• The distinction began to emerge when a clear differentiation was made between chemistry and alchemy by Robert Boyle in his work The Sceptical Chymist (1661)

Answered by Sahdev Sharma (Jul 20, 2017 6:22 p.m.)
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• Robert boyle is the father of chemistry.

Answered by Kriti Bhawsar (Jul 20, 2017 3:26 p.m.)
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In 11.0 is 11 a significant figure or not and why

Posted by Ashutosh Upadhyay (Jul 16, 2017 10:39 p.m.) (Question ID: 6695)

• There are three rules on determining how many significant figures are in a number:

• Non-zero digits are always significant.
• Any zeros between two significant digits are significant.
• A final zero or trailing zeros in the decimal portion ONLY are significant.

So keeping these rules in mind we can say that 11 is significant figure.

Answered by Payal Singh (Jul 20, 2017 6:47 p.m.)
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What is screening effect

Posted by Bntivari Tivari (Jul 12, 2017 9:40 a.m.) (Question ID: 6585)

• Shielding effect can be defined as a reduction in the effective nuclear charge on the electron cloud, due to a difference in the attraction forces of the electrons on the nucleus. It is also referred to as the screening effect (or) atomic shielding.

Answered by Sahdev Sharma (Jul 13, 2017 12:32 a.m.)
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What is difference between molality and molarity

Posted by Akshay Koni (Jul 10, 2017 5:45 p.m.) (Question ID: 6533)

• Molality vs. Molarity:

These two words sound similar but they are not synonyms, even though both of them are used for representing solution concentration. By definition, molarity is the number of moles of solute dissolved per liter of solution. We use capital letter “M” to represent molarity and its formula is M= (# mol SOLUTE)/ (Liters of SOLUTION).

Molality is then the number of moles of solute per kilogram of the SOLVENT, NOT solution! We use lower case letter “m” to represent molality and its formula can be represented as: m= (# mole SOLUTE) / (Kilograms of SOLVENT).

Most of the time scientists use either molarity or molality to represent solution concentration, but MOLALITY is preferred when the temperature of the solution varies. That is because MOLALITY does not depend on temperature, (Neither number of moles of solute nor mass of solvent will be affected by changes of temperature.) while MOLARITY changes as temperature changes. (Volume of solution in the formula changes as temperature changes, and that is why.)

Answered by Jatin Singh (Jul 20, 2017 5:37 p.m.)
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Structure of SO42-

Posted by Allo Taliyan (Jul 09, 2017 11:58 a.m.) (Question ID: 6503)

• https://youtu.be/lEjQKATnI2A

Answered by Jatin Singh (Jul 20, 2017 5:36 p.m.)
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Why chlorine has higher electron gain enthalpy than fluorine

Posted by Uday Bhardwaj (Jul 06, 2017 9:31 a.m.) (Question ID: 6413)

• Chlorine has higher electron gain enthalpy than fluorine because due to small size of fluorine some energy is utilized in overcoming the force of repulsion among electrons. Hence it has lesser value of electron affinity.

Answered by Payal Singh (Jul 06, 2017 1:44 p.m.)
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What is the difference between oxygen gas and dioxygen and their masses?

Posted by Neetu Singh (Jul 03, 2017 10:43 p.m.) (Question ID: 6355)

• Dioxygen means O​​​​​​2 Oxygen basically exists as a diatomic gas, that is two oxygen atoms chemically combine to form an oxygen molecule which is denoted by

O​​​​​​2 In other words, dioxygen is the elemental form of oxygen. So, if in a question only oxygen gas has been mentioned then we will consider O​​​​​​2 and take 32g as the molar mass because atomic mass of oxygen = 16u

So molecular mass of of oxygen gas (O​​​​​​2) = 2 X 16 = 32 u and hence molar mass of oxygen gas = 32g

Otherwise, if oxygen molecule is mentioned, then it is quite clear that you will consider dioxygen and take 32g as the molar mass. However, if in the question specifically oxygen atom has been mentioned, then O atoms will be considered and the molar mass will be taken as 16g, because here we are talking about oxygen atoms, and not oxygen molecules.

Answered by Payal Singh (Jul 04, 2017 6:25 a.m.)
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When water is added, pH of acidic solution...

A) remains same

B) increases

C) decreses

D) becomes zero

Posted by Saurabh Tharu (Jun 24, 2017 5:02 p.m.) (Question ID: 6154)

• Increase

Answered by Dhivya N (Jun 25, 2017 8:44 p.m.)
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• B) Increase

Explanation : When you add pure water to an acidic solution, the solution becomes less acidic and the pH goes up -- to a point. For example, if you add pure water to a relatively acidic solution that has a pH of 3.5, the pH level might go up to a 4 or 5. You cannot, though, turn an acidic solution into a base solution or make it neutral just by adding water. As a result, pure water can only raise the pH of an acidic solution to a maximum of a 6.9.

Answered by Payal Singh (Jun 24, 2017 5:21 p.m.)
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How has Avogadro's hypothesis helped in making distinguish between atom and molecules

Posted by Ayush Gupta (Jun 23, 2017 6:44 p.m.) (Question ID: 6127)

JJ thomson model explain

Posted by Ayush Kumar (Jun 22, 2017 9:09 p.m.) (Question ID: 6105)

• J.J Thomson gave the first model of an atom in which its model is compared with a water melon or Christmas pudding. The reddish part of water melon represents positive charge ( protons ) and seeds embedded in it reflect negative charge ( electrons) . The total amount of positive charge is equal to total amount of negative charge. An atom as a whole is electrically neutral.

Limitations:-

1. This model didn't get experimental support and hence discarded.

2. This model could not explain the stability of an atom as there is no boundary of separation between positive and negative charge

Answered by Trilochan Pathak (Jun 22, 2017 10:48 p.m.)
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Determine all of the quantum number for n=3?

Posted by Pranjali Singh (Jun 17, 2017 3:25 p.m.) (Question ID: 5982)

If the density of 68℅ nitric acid solution is 1.41g ml , calculate the mass of nitric acid present in 1.0 L solution

Posted by Ishika Srivastav (Jun 16, 2017 12:34 p.m.) (Question ID: 5936)

Calculate the mole fraction of nitrogen when 28 g of nitrogen is mixed with 64 g of oxygen gas .

Posted by Ishika Srivastav (Jun 16, 2017 12:03 p.m.) (Question ID: 5933)

Give the name and atomic number of the inert gas atom in which the total number of d-electrons is equal to the difference between the numbers of total p and total s-electrons.

Posted by Sarthak Chauhan (Jun 15, 2017 4:33 p.m.) (Question ID: 5917)

• It is Krypton. Atomic number is 36.

Electronic configuration:

{tex}1s^2 2s^22p^6 3s^23p^64s^23d^{10}4p^6{/tex}

​Number of electrons in s orbital are 8 Number of electrons in p orbital are 18 Number of electrons in d orbitals are 10 (18-8=10)

Answered by Payal Singh (Jun 15, 2017 5:08 p.m.)
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With what velocity should an "alpha" travel toward the nucleus of a copper atom so as to arrive at a distance 10-13meter from the nucleus of the copper atom

Posted by Mukul Sharma (Jun 11, 2017 7:37 p.m.) (Question ID: 5859)

Posted by Mukul Sharma (Jun 11, 2017 7:39 p.m.)

what is NTP and STP???

Posted by Ankit Saini (Jun 09, 2017 10:18 p.m.) (Question ID: 5811)

• STP stands for Standard Temperature and Pressure.
NTP stands for Normal Temperature and Pressure.

At STP: Pressure = 1 bar = 0.987 atm
Temperature = 273 K or 0°C

At NTP: Pressure = 1 atm
Temperature = 293 K or 20°C

Answered by Shweta Gulati (Jun 10, 2017 12:59 a.m.)
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Which of the following is acidic oxide?

a)Na2O

b)MgO

c)Cao

d)so2

Posted by Rajiv Nepal (Jun 08, 2017 8:51 p.m.) (Question ID: 5770)

• d) SO2

Answered by Payal Singh (Jun 08, 2017 10:19 p.m.)
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Which of the following is not a polymer?

a)protein

b)Fructose

C)Rubber

d)Cellulose

Posted by Rajiv Nepal (Jun 08, 2017 8:48 p.m.) (Question ID: 5769)

• b)Fructose

Answered by Payal Singh (Jun 08, 2017 10:20 p.m.)
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Silicon is an important constituent of

a) chlorophyll

b)Heamoglobin

c)Rocks

d)Amalgams

Posted by Rajiv Nepal (Jun 08, 2017 8:46 p.m.) (Question ID: 5768)

• Rocks

Answered by Payal Singh (Jun 08, 2017 10:16 p.m.)
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Which is not a natural polymer?                      Wool

Silk

Leather

Nylon

Posted by Rajiv Nepal (Jun 08, 2017 8:44 p.m.) (Question ID: 5767)

• Nylon

Answered by Payal Singh (Jun 08, 2017 10:14 p.m.)
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The number of waves made by a bhor electron in an orbit of maximum magnetic quantum number +2.....

Posted by Ishwar Tiwari (Jun 07, 2017 11:13 p.m.) (Question ID: 5739)

• No of waves are 3

Answered by Payal Singh (Jun 08, 2017 8:27 a.m.)
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A part A is moving with a certain velocity has a de broglie wavelength of 10 raised to the power -10. If the particle B has a mass 25percent of that A and velocity 75percent of that of A,  the de broglie wavelength of B will be approximately...

Posted by Ishwar Tiwari (Jun 07, 2017 8:24 a.m.) (Question ID: 5728)

If the total energy of an electron in a hydrogen like atom in excited state is -3.4ev, then the de broglie wavelength of the electron is....

Posted by Ishwar Tiwari (Jun 07, 2017 8:22 a.m.) (Question ID: 5727)

Calculate the de broglie wavelength of the electron in the ground state of hydrogen atom, given that it is kinetic energy is 13.6ev...

Posted by Ishwar Tiwari (Jun 07, 2017 8:19 a.m.) (Question ID: 5726)

A helium molecule is moving with a velocity of 2.40multiply 10 raised to the power 2ms at 300k. The de broglie wavelength is about....

Posted by Ishwar Tiwari (Jun 07, 2017 8:18 a.m.) (Question ID: 5725)

Two particles A and B are in motion.  If the wavelength associated with the particle A is 5 multiply 10 raised to power -8 m, the wavelength of particle B having momentum half of A is....

Posted by Ishwar Tiwari (Jun 07, 2017 7:22 a.m.) (Question ID: 5724)

• {tex}(mV)_A={h\over λ_A }{/tex}

{tex}(mV)_B={h\over λ_B }{/tex}

{tex}(mV)_B={1\over 2}(mV)_A {/tex}   [Given]

{tex}{h\over λ_B}={1\over 2}\times {h\over λ_A }{/tex}

{tex}λ_B=2λ_A {/tex}

=2×5×10−8

=10×10−8m

=1000A

Answered by Payal Singh (Jun 07, 2017 8:02 a.m.)
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