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Standard enthalpy of formation

Posted by Mohammad Saad 7 years ago

CBSE > Class 11 > Chemistry

1 answers

Ayushi Ayushi 7 years ago

The standard enthalpy of formation is a measure of the energy released or consumed when one mole of a substance is created under standard conditions from its pure elements. The symbol of the standard enthalpy of formation is ΔHf. Δ = A change in enthalpy o = A degree signifies that it's a standard enthalpy change. f = The f indicates that the substance is formed from its elements The equation for the standard enthalpy change of formation (originating from Enthalpy's being a State Function), shown below, is commonly used: ΔHoreaction=∑ΔHof(products)−∑ΔHof(Reactants)(1.1) (1.1)ΔHreactiono=∑ΔHfo(products)−∑ΔHfo(Reactants) This equation essentially states that the standard enthalpy change of formation is equal to the sum of the standard enthalpies of formation of the products minus the sum of the standard enthalpies of formation of the reactants.

ANSWER

Define pH. What is its value for neutral water at 25 degree Celcius?

Posted by Ishita Ishita 7 years ago

CBSE > Class 11 > Chemistry

4 answers

Ishita Ishita 7 years ago

What!!!!!!!Is it presence of hydrogen...omg??

Om Wadolkar 7 years ago

Hp means presense of hydrogen

Anurag Rana 7 years ago

hyy

Ayushi Ayushi 7 years ago

pH is a measure of hydrogen ion concentration, a measure of the acidity or alkalinity of a solution. The pH scale usually ranges from 0 to 14. Aqueous solutions at 25°C with a pH less than 7 are acidic, while those with a pH greater than 7 are basic or alkaline. A pH level of 7.0 at 25°C is defined as "neutral" because the concentration of H3O+ equals the concentration of OH− in pure water. Very strong acids might have a negative pH, while very strong bases might have a pH greater than 14.

ANSWER

What is the importance of ultra-pure elemental silicon? How is it obtained?

Posted by Ishita Ishita 7 years ago

CBSE > Class 11 > Chemistry

0 answers

ANSWER

The salt of strong acid and strong base does not undergo hydrolysis.Comment.

Posted by Ishita Ishita 7 years ago

CBSE > Class 11 > Chemistry

3 answers

Saba Elias 7 years ago

Ur welcome

Ishita Ishita 7 years ago

Thanks

Saba Elias 7 years ago

In this case neither cation nor anion undergo hydrolysis. Therefore the solution remains neutral. For example in the aqueous solution of NACL its ions Na+and Cl- have no tendency to react with the H+ or OH- ions of water.this is because the possible products of such reaction are NaOH and HCL which are themselves completely dissociated. As a result.,there is no change in the concentration of H+ and OH- ions and hence the solution continues to remains neutral

ANSWER

(CH)3N is basic but (CF3)3N is not basic.Explain.

Posted by Ishita Ishita 7 years ago

CBSE > Class 11 > Chemistry

2 answers

Ishita Ishita 7 years ago

Thank u

Harsh Mishra 7 years ago

Fluorine is more electronegative than hydrogen is. It polarises the covalent bond that forms between it and the carbon atom in (CF3)3N.

ANSWER

Potassium carbonate cannot be prepared by Solvay process.Why.

Posted by Ishita Ishita 7 years ago

CBSE > Class 11 > Chemistry

5 answers

Ankit Singh 7 years ago

Thanks ishita sunn ke aacha laga

Ishita Ishita 7 years ago

Of course ur answers r always helping me???

Ankit Singh 7 years ago

Hope this answer help u

Ankit Singh 7 years ago

Solvay process cannot be used to prepare potassium carbonate. This is because unlike sodium bicarbonate, potassium bicarbonate is fairly soluble in water and does not precipitate out.

Pragati Gola 7 years ago

As K2CO3 is to soluble which can not be precipitated out

ANSWER

Why fqlling liquid drops are spherical?

Posted by Ishita Ishita 7 years ago

CBSE > Class 11 > Chemistry

6 answers

Shruti Gupta 7 years ago

Every body on earth surface aquire min. Surface area and we know that the sphere has min. Surface area

Priya Dharshini ☺☺ 7 years ago

It is due to surface tension

Saba Elias 7 years ago

Welcome

Ishita Ishita 7 years ago

Thnk u for ur answers

Ayushi Ayushi 7 years ago

Falling drop of a liquid is always spherical in shape due to surface tension. The inward forces on the surface molecules of the liquid droplet tend to cause the surface to volume ratio as small as possible.

Saba Elias 7 years ago

Due to surface tension . Surface tension is a property of liquid by which surface molecules of a liquid tries to hold the molecules together by acquiring minimum Surfacr area in acting like a stretched membrane

ANSWER

What does the equilibrium constant K less than 1 indicates?

Posted by Ishita Ishita 7 years ago

CBSE > Class 11 > Chemistry

4 answers

Pragati Gola 7 years ago

Equilibrium shifted towards forward

Ayushi Ayushi 7 years ago

Your wellcome

Ishita Ishita 7 years ago

Thnk u

Ayushi Ayushi 7 years ago

. If K is larger than 1, the mixture contains mostly products. If K is less than 1, the mixture contains mostly reactants.

ANSWER

What is absorption chromatography?

Posted by Prakhar Jadaun ? 7 years ago

CBSE > Class 11 > Chemistry

1 answers

Yogita Ingle 7 years ago

Adsorption chromatography: In the process of adsorption chromatography, different compounds are adsorbed on the adsorbent to different degrees based on the absorptivity of the component. Here also, a mobile phase is made to move over a stationary phase, thus carrying the components with higher absorptivity to a lower distance than that with lower absorptivity.

ANSWER

What is the use of a frationating column?

Posted by Prakhar Jadaun ? 7 years ago

CBSE > Class 11 > Chemistry

1 answers

Yogita Ingle 7 years ago

Fractionation Column is basically a diffrentated chamber that have different range of temperature i.e different boiling points, in case of separation of petroleum mixture temperature goes on increasing from top to bottom of the column.
Thus, In fractional distillation , that component separates first which have least boiling point and finally that component having highest boiling point.

The Fractionating Column use for the Separation of Fatty Acids.

ANSWER

In the formation of sodium chloride , sodium reacts with Cl or Cl2

Posted by Akash Kushwaha 7 years ago

CBSE > Class 11 > Chemistry

4 answers

Aditi Mittal 7 years ago

Which a cl needs only..

Aditi Mittal 7 years ago

Na react with cl because Na gives 1 electron to Cl.

Akash Kushwaha 7 years ago

How one Na atom can react with two Cl atoms ?

Chesta Pawan Manchanda 7 years ago

2Na+cl2------------2NaCl

ANSWER

Ch3single bond C triple Bond C single bond H+H single bond O single bond H in presence of H2SO4,HGLO4 ?toutomerism?

Posted by Sks Khan 7 years ago

CBSE > Class 11 > Chemistry

0 answers

ANSWER

Who is cbse chairman?

Posted by Christin Mathew 7 years ago

CBSE > Class 11 > Chemistry

6 answers

Ankit Singh 7 years ago

????

Priya Dharshini ☺☺ 7 years ago

Anita karwal IAS....

Ritu Thapliyal 7 years ago

Anita Karwal

Yakshi ? 7 years ago

Why are u asking????

???. Pragati 7 years ago

I think anita karwal

Christin Mathew 7 years ago

Is it Mr vineet joshi

ANSWER

Define the Nucleophiles?

Posted by Jasmine Jasmine 7 years ago

CBSE > Class 11 > Chemistry

3 answers

Jasmine Jasmine 7 years ago

Species which are attract towards electron dificient species are called nucleophiles.

Jasmine Jasmine 7 years ago

No ishita ??

Ishita Ishita 7 years ago

Hlo jasmine ur class incharge is Mr. Gagandeep Garg....m i right....???

ANSWER

What is degree of disassociation frm ch. Equilibrium❔ N plz tell weather this topic is in NCERT or not...

Posted by ♥️Bhavika Naik?? 7 years ago

CBSE > Class 11 > Chemistry

2 answers

Jatin Choudhary 7 years ago

Number of mole dissociate/ total number of mole

Aditi Mittal 7 years ago

It is the ratio of total number of moles desociate into ions with the total number of moles taken..

ANSWER

Iupac naming of 2-ethyl-but-1-ene obtain by ozonolysis

Posted by Abhi Kamboj 7 years ago

CBSE > Class 11 > Chemistry

1 answers

Shubham Singh 7 years ago

??

ANSWER

A cylinder of cooking gas is assumed to contain 11.2kg

Posted by Nirupama Thakur 7 years ago

CBSE > Class 11 > Chemistry

2 answers

Christin Mathew 7 years ago

Yes ??????

Deepanshi Garg 7 years ago

2 things- 1) Actually it contains 14 kg of LPG. 2) What is your question btw❓❓❓???

ANSWER

Can you describe me free radical with examples?

Posted by Ayushi Ayushi 7 years ago

CBSE > Class 11 > Chemistry

6 answers

Ankit Singh 7 years ago

Yours welcome ???

Ayushi Ayushi 7 years ago

Ankit your answer is suitable for me to discribe free radical with examples. And thanks for the answer.

Ayushi Ayushi 7 years ago

Thanks

Ankit Singh 7 years ago

Free radical, is the term used to describe a particle that has an unpaired electron. An electron is the negative portion of an atom and is found outside the nucleus, or the center of the atom. As you can see from the image on screen of the Lithium atom, electrons can be found close to the nucleus or far away from the nucleus. For this lesson, we're going to focus on the valence electrons, which are the electrons furthest away from the nucleus, and the electrons most likely to be involved in reactions. For example :Let's say you have two chlorine atoms that are bonded or stuck, together making a molecule. Given enough heat, these two chlorines will break apart and each will end up taking their valence electrons with them. You can see from the image that each has seven valence electrons. Now each one has an unpaired valence electron. Uh oh! You know what that means. Yep, they're free radicals. And they are very reactive and, since electrons don't like being unpaired, they will try to find another particle to react with.

Gaurav Seth 7 years ago

Free redicals:

free radical, in chemistry means , a molecule or atom that contains an unpaired electron but is neither positively nor negatively charged. Free radicals are usually highly reactive and unstable. They are produced by homolytic cleavage of a covalent bond (see chemical bond); i.e., each of the atoms connected by the bond retains one of the two electrons making up the bond. The homolytic cleavage of a hydrogen molecule, H2, produces two hydrogen free radicals (hydrogen atoms). Similarly, two chlorine free radicals can be produced from a chlorine molecule. Homolytic cleavage of the carbon-bromine bond in methyl bromide, CH3Br, would produce a methyl free radical and a bromine free radical. The term free is often dropped in referring to free radicals; this could lead to confusion if the term radical were used synonymously with group in organic chemistry, e.g., by calling an alkyl group an alkyl radical when free radical was not intended.

Ayushi Ayushi 7 years ago

I searched it on Google but I don't understand so can anyone help me to complete my project?

ANSWER

Mechanism of halogenation ....i mean chain termination of alkanes....plz explain

Posted by Yakshi ? 7 years ago

CBSE > Class 11 > Chemistry

3 answers

Yakshi ? 7 years ago

Obviously...... ??????

Ankit Singh 7 years ago

I think this answer will help u

Ankit Singh 7 years ago

· A chain reaction mechanism for the chlorination of methane has been described. Bromination of alkanes occurs by a similar mechanism, but is slower and more selective because a bromine atom is a less reactive hydrogen abstraction agent than a chlorine atom, as reflected by the higher bond energy of H-Cl than H-Br.

ANSWER

How to find the charge of an element from the compound?

Posted by Aradhya Gupta 7 years ago

CBSE > Class 11 > Chemistry

4 answers

Nidhi Shukla 7 years ago

This is known as oxidation number which you are asking

Prince Neeraj 7 years ago

From its valency

Yakshi ? 7 years ago

I think u are asking for oxidation no. Am i right???

Christin Mathew 7 years ago

?no idea

ANSWER

Electron filling of fluorine molecule?

Posted by Aditi Mittal 7 years ago

CBSE > Class 11 > Chemistry

4 answers

Aditi Mittal 7 years ago

Guys can't u understand.it is the question from molecular orbital theory concept..

Pragati Gola 7 years ago

[He]2s^2 2p^5

Aditi Mittal 7 years ago

Actually I asked of molecule not atom...

Nidhi Shukla 7 years ago

2,7

ANSWER

Easy Define of Inert pair effect....

Posted by Hritik Gupta 7 years ago

CBSE > Class 11 > Chemistry

1 answers

Lily ☺ 7 years ago

The non participation of ns electron in bonding

ANSWER

Nitrogen dioxide can not be obtained by heating

Posted by Muskan Khatter 7 years ago

CBSE > Class 11 > Chemistry

1 answers

Sivan Karthick 7 years ago

because nitrogen is most unreactive gas due to its half filed electronic configuration so nitrogen dioxide cannot be obtained by heating

ANSWER

What is le chaterials law

Posted by Saket Kumar Thakur 7 years ago

CBSE > Class 11 > Chemistry

1 answers

Bhaskar Sharma 7 years ago

In equillibrium if any factor disturb equillibrium then the shift it to regain equillibirium or to counter it.

ANSWER

Explain Nucleophilic with examples?

Posted by Ayushi Ayushi 7 years ago

CBSE > Class 11 > Chemistry

3 answers

Yakshi ? 7 years ago

Wlcm......???

Ayushi Ayushi 7 years ago

Thanks

Yakshi ? 7 years ago

Nucleophiles are electron rich species.either -vely charged or neutral molecules having lone pair electrons.....example...OH- , CN-

ANSWER

What is Grahams law of diffusion ?? Please explain simple form

Posted by Ankit Singh 7 years ago

CBSE > Class 11 > Chemistry

5 answers

Priya Dharshini ☺☺ 7 years ago

Ur wlcm?

Ankit Singh 7 years ago

Thanks Priya ???

Priya Dharshini ☺☺ 7 years ago

the rates of effusion of two gases are inversely proportional to the square roots of their molar masses at the same temperature and pressure

Sivan Karthick 7 years ago

r divided by R= square root of T÷t

Ankit Singh 7 years ago

Please give the answer

ANSWER

No of molecule in 16 gm oxygen

Posted by Yogendra Singh Thakur 7 years ago

CBSE > Class 11 > Chemistry

1 answers

Durgesh Jeengar 7 years ago

No of molecule=given mass×Na/molar mass{Na=6.023*10*23} Molar mass of oxygen=2*16 = 32 According to formula=16×6.023*10*23÷32 =3.0115*10*23 molecules

ANSWER

What is group oxidation state? I want its definition.

Posted by Divya Tripathy 7 years ago

CBSE > Class 11 > Chemistry

2 answers

Divya Tripathy 7 years ago

Thanks ?

Yogita Ingle 7 years ago

The general valence shell electronic configuration of p-block elements is ns² np^1-6 where n=2-6.
The highest oxidation state of the elements of p-block is numerically equal to group number minus 10 or number of valence electrons. This highest oxidation state exhibited by all the elements in a particular group is known as group oxidation state. For example , For 13 group , Group number =13
Highest oxidation state=13-10=+3
Therefore, group 13 elements have +3 group oxidation state.

ANSWER

Why co2 is a gas and sio2 is solid

Posted by Atul Kumar 7 years ago

CBSE > Class 11 > Chemistry

2 answers

Sanidhya Jadaun? 7 years ago

As carbon and silicon are of same group, but carbon comes first and silicon second. As we know when we goes down a group , size of the elements increases , so they prefer to make sigma bond rather than pie bond. So carbon makes pie bond with oxygen and as we all know pie bonds are weak so co2 is a gas. But in case of SiO2 it makes sigma bond with oxygen and due to strong bond SiO2 is solid . For more clearance please the structure of SiO2 in ncert 2nd textbook , chapter p block.

Divya Tripathy 7 years ago

It is all due to vander wall forces. The CO2 has less intermolecular forces. The sio2 has strong intermolecular forces or vander wall forces due to which it binds its molecules or atoms. So therefore sio2 is solid

ANSWER

one mole of pcl5 is heated one litre of closed container if 0.5 mole of chloride is found at equilibrium calculate the value of of equilibrium constant

Posted by Nancy Rajput 7 years, 1 month ago

CBSE > Class 11 > Chemistry

0 answers

ANSWER

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