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Sanjay 20/05/2016 in  IIT JEE Coaching classes

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Swagata replied | 29/05/2016

a mixture of dyes that changes colour gradually over a range of pH and is used (especially as indicator paper) in testing for acids and alkalis.

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Oasis Gurgaon replied | 29/05/2016

A universal indicator is a solution which undergoes several color changes over a wide range of pH's. The color is used to "indicate" pH directly. Universal indicators are usually mixtures of several indicators.

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Maheshwari 20/05/2016 in  IIT JEE Coaching classes

What is methyl orange? How is it made?

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Kamal replied | 21/05/2016

Methyl orange is a pH indicator frequently used in titrations because of its clear and distinct colour change. Because it changes colour at the pH of a midstrength acid, it is usually used in titrations for acids.

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Swagata replied | 29/05/2016

Methyl orange is an intensely colored compound used in dyeing and printing textiles. It is also known as C.I. Acid Orange 52, C.I. 13025, helianthine B, Orange III, Gold orange, and Tropaeolin D . Chemists use methyl orange as an indicator in the titration of weak bases with strong acids.

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Soumya 20/05/2016 in  IIT JEE Coaching classes

What are some natural acid/base indicators?

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Nimesh replied | 24/05/2016

Many flowers,fruits,vegtables are natural indicators. One such example is rose anthocyanins.

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Swagata replied | 29/05/2016

Many flowers, fruits and vegetables contain chemical substances that change color in solutions of different pH. acid or base natural indicator, such as hibiscus, turmeric, red cabbage, and some other kinds of plants. Many indicators have been extracted from plants.

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Hima 20/05/2016 in  IIT JEE Coaching classes

What household substances can be used as acid/base indicators?

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Jayasimha replied | 20/05/2016

Carrots
Cherries and cherry juice is bright red in acidic solution but purple to blue in basic solution.
Cranberries
Curry powder and tumeric are spices that contain a bright yellow pigment called curcumin (which is not an anthocyanin). It turns from yellow at pH 7.4 to red at pH 8.6.
Delphinium petals contain an anthocyanin called delphinin, which changes from...  more»
Carrots
Cherries and cherry juice is bright red in acidic solution but purple to blue in basic solution.
Cranberries
Curry powder and tumeric are spices that contain a bright yellow pigment called curcumin (which is not an anthocyanin). It turns from yellow at pH 7.4 to red at pH 8.6.
Delphinium petals contain an anthocyanin called delphinin, which changes from bluish red in acid to blue to violet in basic solution.
Red cabbage contains a mixture of anthocyanins and other pigments that indicate a wide range of pH. The photograph at right shows how red cabbage juice changes from deep red at pH 1 to purple at pH 7 to to green at pH 12. At higher pH (13-14) it turns yellow.
Red radish
Rhubarb
Rose petals contain the oxonium salt of cyanin, and they turn blue in basic solution. (The potassium or calcium salt of the same pigment makes cornflowers blue!)
Strawberries
Tea «less

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Swagata replied | 29/05/2016

Here's a partial list of house and garden materials that can be used as acid/base indicators. Notice that most of the materials are derived from plants. Almost any flower, fruit, or plant part that is red, blue, or purple contains a class of chemical compounds called anthocyanins that change color with pH.

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Boyina.bala 20/05/2016 in  IIT JEE Coaching classes

What are some novel ways to use indicators (besides titrations)?

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Jayasimha replied | 20/05/2016

Mood lipstick. Acid-base indicators in the cosmetics change color on application due to skin pH.
Turning "water" to "wine". Add phenolpthalein to a clear dilute NaOH solution.)
Making real wines red. Red wines contain anthocyanins, which are pH indicators. Adjusting the pH of the wine changes its color (and its taste). Welch's grape juice works, too.
Disappearing...  more»
Mood lipstick. Acid-base indicators in the cosmetics change color on application due to skin pH.
Turning "water" to "wine". Add phenolpthalein to a clear dilute NaOH solution.)
Making real wines red. Red wines contain anthocyanins, which are pH indicators. Adjusting the pH of the wine changes its color (and its taste). Welch's grape juice works, too.
Disappearing ink and invisible ink Write a message in colorless phenolthalein. Spray the paper with a dilute NaOH solution and the letters appear in pink.
Demonstrating how an ion exchange column works (see the July 1996 issue of the Journal of Chemical Education for more).
Food coloring
Monitoring swimming pool pH. «less

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Swagata replied | 29/05/2016

Mood lipstick. Acid-base indicators in the cosmetics change color on application due to skin pH.
Turning "water" to "wine". Add phenolpthalein to a clear dilute NaOH solution.)
Making real wines red. Red wines contain anthocyanins, which are pH indicators. Adjusting the pH of the wine changes its color (and its taste). Welch's grape juice works, too.
Disappearing...  more»
Mood lipstick. Acid-base indicators in the cosmetics change color on application due to skin pH.
Turning "water" to "wine". Add phenolpthalein to a clear dilute NaOH solution.)
Making real wines red. Red wines contain anthocyanins, which are pH indicators. Adjusting the pH of the wine changes its color (and its taste). Welch's grape juice works, too.
Disappearing ink and invisible ink Write a message in colorless phenolthalein. Spray the paper with a dilute NaOH solution and the letters appear in pink.
Demonstrating how an ion exchange column works (see the July 1996 issue of the Journal of Chemical Education for more).
Food coloring
Monitoring swimming pool pH.
Soil pH kits.
Demonstrating the electrolysis of water
Making a "voice activated" chemical reaction. (a solution of phenol red in very slightly alkaline water will turn from red to yellow, if you talk to it for a while :) Carbon dioxide from your breath neutralizes the solution and causes the color change. «less

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Laxmi 19/05/2016 in  IIT JEE Coaching classes

Why is atomic number called "Z"? Why is mass number called "A"?

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Nakshatratuitions And Educational Academy replied | 25/05/2016

Index and bases so

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Swagata replied | 29/05/2016

"Atomic number" in German is "Atomzahl", so the Z symbol for atomic number probably comes from "Zahl" (number).

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Vg.manikandan 19/05/2016 in  IIT JEE Coaching classes

How do I know that atoms really exist?

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Jayasimha replied | 19/05/2016

Today, we can not only "see" individual atoms on surfaces- we can also move them from place to place, and build things from them. The strongest evidence for the reality of atoms comes from scanning tunneling microscopy, studies of Brownian motion, and by the remarkably good agreement for experimental estimates of Avogadro's Number.

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Swagata replied | 29/05/2016

In the early years of the twentieth century, atoms were still theoretical entities. Strong circumstantial evidence suggested that atoms existed, but no one had ever actually seen an atom. Today, we can not only "see" individual atoms on surfaces- we can also move them from place to place, and build things from them. The strongest evidence for the reality of atoms comes from scanning...  more»
In the early years of the twentieth century, atoms were still theoretical entities. Strong circumstantial evidence suggested that atoms existed, but no one had ever actually seen an atom. Today, we can not only "see" individual atoms on surfaces- we can also move them from place to place, and build things from them. The strongest evidence for the reality of atoms comes from scanning tunneling microscopy, studies of Brownian motion, and by the remarkably good agreement for experimental estimates of Avogadro's Number.
Scanning tunneling microscopy. Pictures of atoms can be taken by placing the tip of very sharp needle just above a sample surface. A very small voltage is applied to cause electrons to "tunnel" from the tip to the surface. As the tip is dragged over an atom on the surface, more electrons tunnel and the needle is rigged so that the increase in current causes the tip to move up. As the tip is dragged off the atom, the distance between the tip and the surface widens, causing a decrease in current which moves the tip down. The tip height can be monitored to build an image of the actual shape and features of the sample surface on the atomic scale.
Seeing is believing. The STM Image Gallery at IBM's Almaden Research Center contains many pictures of atoms taken with a the scanning tunneling microscope.

Brownian movement. Botanist Robert Brown noticed that tiny objects like pollen grains shook and moved erratically when viewed under a microscope. Nearly seventy years later, Albert Einstein explained this "Brownian motion" as the result of bombardment by molecules. His explanation was quantitative; he was able to mathematically estimate the average distance that the particles should be moved over time as a result of molecular bombardment. A few years later Jean Perrin painstakingly measured the displacements of particles of a resin suspended in water; his experimental average displacement was in excellent agreement with Einstein's theoretical prediction.
Avogadro's number. Avogadro's number is the number of molecules in one mole of any compound. There are dozens of different experimental methods for measuring Avogadro's number. All give the same result. The fact that Avogadro's number seems to be independent of any particular method implies that it actually has meaning- and so is strong circumstantial evidence that molecules actually exist. «less

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Shagufta 19/05/2016 in  IIT JEE Coaching classes

How were atomic masses measured before mass spectrometry?

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Swagata replied | 29/05/2016

This useful fact allowed chemists to compare the relative weights of equal volumes of different gases to determine the relative masses of the atoms composing them. They measured atomic weights in terms of atomic mass units (u), where 1 u was equal to one-twelfth of the mass of a carbon-12 atom.

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Shivaji replied | 10/06/2016

This useful fact allowed chemists to compare the relative weights of equal volumes of different gases to determine the relative masses of the atoms composing them. They measured atomic weights in terms of atomic mass units (u), where 1 u was equal to one-twelfth of the mass of a carbon-12 atom

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Vishal 19/05/2016 in  IIT JEE Coaching classes

How many excess electrons does an oil droplet contain, given its charge?

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Swagata replied | 29/05/2016

Suppose you wanted to figure out how many Hershey's kisses you get in a one-pound bag. If you knew that one kiss weighed 22.7 g, you could find the number of kisses as
1 kiss
22.7 g 454 g
1 pound = 20 kisses per 1 lb. bag

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Shivaji replied | 10/06/2016

charge of -4.8 x 10^(-19) C. Q = ne • -4.8 x 10^(-19) C = n(1.6 x 10^(-19) • n = -4.8 x 10^(-19)/1.6 x 10^(-19) = 3 electrons

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Somil 19/05/2016 in  IIT JEE Coaching classes

What indicators change from clear to colored?

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Jayasimha replied | 19/05/2016

Phenolpthalein turns from clear in neutral solution to pink in alkaline solution.

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Swagata replied | 29/05/2016

Phenolpthalein turns from clear in neutral solution to pink in alkaline solution. An old trick is to pour a phenolpthalein solution into a cup containing a little sodium hydroxide; the result is an apparent transformation of 'water' into 'wine'.

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Ravikumar 18/05/2016 in  IIT JEE Coaching classes

How do you find the number of neutrons in an atom?

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Jayasimha replied | 19/05/2016

If you know the mass number and atomic number of the atom, the number of neutrons is just the difference between them. For example, in a carbon-13 atom, the atomic number is six and the mass number is thirteen, so the number of neutrons is seven.

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Swagata replied | 29/05/2016

If you know the mass number and atomic number of the atom, the number of neutrons is just the difference between them.

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Renu 18/05/2016 in  IIT JEE Coaching classes

Do movements of electrons and of nuclei affect each other?

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Jayasimha replied | 19/05/2016

Yes, the electrons tug on the nucleus, and the nucleus tugs on the electrons, so their motions affect each other. But it's a very small effect because the nuclei are at least 3 orders of magnitude more massive than the electrons. We usually get away with assuming that the nuclei are clamped in place, while the electrons roam freely around and among them.

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Swagata replied | 29/05/2016

Yes, the electrons tug on the nucleus, and the nucleus tugs on the electrons, so their motions affect each other. But it's a very small effect because the nuclei are at least 3 orders of magnitude more massive than the electrons. We usually get away with assuming that the nuclei are clamped in place, while the electrons roam freely around and among them.

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Sitaram 18/05/2016 in  IIT JEE Coaching classes

What is a "dalton"?

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Jayasimha replied | 19/05/2016

The unified atomic mass unit (symbol: u) or dalton (symbol: Da) is the standard unit that is used for indicating mass on an atomic or molecular scale (atomic mass). One unified atomic mass unit is approximately the mass of one nucleon (either a single proton or neutron) and is numerically equivalent to 1 g/mol.

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Swagata replied | 29/05/2016

a unit used in expressing the molecular weight of proteins, equivalent to atomic mass unit.

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Neha 18/05/2016 in  IIT JEE Coaching classes

What are alpha particles?

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Dinesh replied | 25/05/2016

its fast moving packet containing 2 neutrons and 2 protons. its like helium nucleus .

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Ramaannuujam replied | 30/05/2016

Nucleus of helium is called alpha particle.

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Prerana 18/05/2016 in  IIT JEE Coaching classes

What is thiosulfate ion, and what is it used for?

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Jayasimha replied | 19/05/2016

Thiosulfate (S2O32-) is an oxyanion of sulfur produced by the reaction of sulfite ions with elemental sulfur in boiling water.USES :As photographic fixing agent.2. For extracting silver from ores 3.For manufacture of Paper and dechlorination of water.4.For determining dissolved oxygen and chemical analysis of oxidants 5. For Whitening cotton fabrics, bone, straw, and ivory.

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Shivaji replied | 10/06/2016

Thiosulfate (S2O32-) is an oxyanion of sulfur produced by the reaction of sulfite ions with elemental sulfur in boiling water,
S(s) + SO32-(aq) S2O3-2(aq)
Thiosulfate is a reducing agent. It is routinely used as a titrant to determine concentrations of oxidants such as hypochlorite in bleach and dissolved oxygen in water. It instantly dechlorinates water, and is used...  more»
Thiosulfate (S2O32-) is an oxyanion of sulfur produced by the reaction of sulfite ions with elemental sulfur in boiling water,
S(s) + SO32-(aq) S2O3-2(aq)
Thiosulfate is a reducing agent. It is routinely used as a titrant to determine concentrations of oxidants such as hypochlorite in bleach and dissolved oxygen in water. It instantly dechlorinates water, and is used to stop bleaching action in the paper-making industry. «less

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Siraj 17/05/2016 in  IIT JEE Coaching classes

Can a compound be classified as ionic or molecular from its formula alone?

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Jayasimha replied | 19/05/2016

No. Not always. But there is a rule of thumb that makes it easy to recognize many compounds as ionic.
Compounds that contain both metals and nonmetals are usually ionic. For example, Na2SO4 contains a metal (Na) and nonmetals (sulfur and oxygen), and so is expected to be ionic. But CO2 and CH4 contain only nonmetals, and are expected to be molecular compounds.

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Shivaji replied | 15/06/2016

No. Not always. But there is a rule of thumb that makes it easy to recognize many compounds as ionic

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Balendra 17/05/2016 in  IIT JEE Coaching classes

What properties distinguish ionic compounds from covalent compounds?

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Jayasimha replied | 19/05/2016

1.Electrical conductivity of the compound in aqueous solution.2.Electrical conductivity of the compound in liquid form.3.Hardness 4.Melting points and boiling points5.Enthalpies of fusion and vaporization

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Shivaji replied | 10/06/2016

Electrical conductivity of the compound in aqueous solution. ...
Electrical conductivity of the compound in liquid form. ...
Hardness. ...
Melting points and boiling points.

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Praveen 17/05/2016 in  IIT JEE Coaching classes

What is a binary compound?

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Mohit replied | 17/05/2016

A binary compound is a chemical compound that contains exactly two different type of elements. Examples : calcium chloride, sodium fluoride, and magnesium oxide

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Jayasimha replied | 19/05/2016

Binary means "two". A binary compound contains two different elements, chemically bound together.

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Raghav 17/05/2016 in  IIT JEE Coaching classes

What is a compound?

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Kamal replied | 17/05/2016

A compound is a substance formed when two or more chemical elements are chemically bonded together

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Jayasimha replied | 19/05/2016

Compounds are pure substances made of atoms of two or more elements chemically combined in fixed ratios.

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Parini 17/05/2016 in  IIT JEE Coaching classes

What is a carbonate, and what is it used for?

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Jayasimha replied | 19/05/2016

A carbonate is a compound that contains the CO32- ion. Inorganic carbonates are ionic compounds that combine metal cations with the carbonate ion.USES:1.Soda ash (Na2CO3), or sodium carbonate, is used in the manufacture of glass, paper, rayon, soaps, and detergents.2.Limestone (CaCO3) is used in refining iron ore and manufacturing steel, making agricultural lime, making cement,...  more»
A carbonate is a compound that contains the CO32- ion. Inorganic carbonates are ionic compounds that combine metal cations with the carbonate ion.USES:1.Soda ash (Na2CO3), or sodium carbonate, is used in the manufacture of glass, paper, rayon, soaps, and detergents.2.Limestone (CaCO3) is used in refining iron ore and manufacturing steel, making agricultural lime, making cement, in scrubbers that remove sulfur from flue gases, and the manufacture of soda ash.3.Potash (K2CO3), or potassium carbonate, is used in the manufacture of glass.
4.Lithium carbonate (Li2CO3) is used in the production of glasses, ceramics, pharmaceuticals, and aluminum.
5.Strontium carbonate (SrCO3) is used to manufacture CRT tubes for televisions and computers. It also is used in red fireworks.
6.Nickel carbonate (NiCO3) is used in electroplating and in the manufacture of ceramics.
7.Cobalt carbonate (CoCO3) is used as a catalyst in the refining industry, as a ceramic pigment, and as a mineral supplement for livestock. «less

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Shivaji replied | 10/06/2016

A carbonate is a compound that contains the CO32- ion. Inorganic carbonates are ionic compounds that combine metal cations with the carbonate ion
It is also used as a water softener, since carbonate can precipitate the calcium and magnesium ions present in "hard" water. Soda ash is also used to control pH (carbonate solutions neutralize acids, producing only carbon dioxide and water

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Nasreen 16/05/2016 in  IIT JEE Coaching classes

Can you predict the formulas for binary covalent compounds?

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Batchu Rohith replied | 06/07/2016

yes u can easily predict

1.By two compounds which are different
2.When last compund is anion we can confirm it is binary covalent compund Ex:ClF3,ZnF,
3.formula ending with " ide " we can say it is binary covalent compound

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Narendra Kumar replied | 09/07/2016

(CH3OH)

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S 16/05/2016 in  IIT JEE Coaching classes

Where can I find the structure of a compound from its name or formula?

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Chaitanya replied | 07/06/2016

NIST Chemistry webbook

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Alpine replied | 05/07/2016

there are some books, for organic : O.P. Tondon , Cengege; Inorganic : O.P. Tondon

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Aneesh 16/05/2016 in  IIT JEE Coaching classes

Why is the anion suffix -ide used to name molecular compounds?

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Shivaji replied | 04/06/2016

Simple acids, known as binary acids, have only one anion and one hydrogen. These anions usually have the ending "-ide.

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Ravindra Kumar replied | 08/06/2016

Because anion have high electron negativity than positive ion in molecular compound and therefore, as per IUPAC nomenclaure used suffix of high EN element.

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Non 16/05/2016 in  IIT JEE Coaching classes

Where can I find the name for a specific compound, given only its molecular formula?

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Shivaji replied | 04/06/2016

CS ChemFinder by Cambridge Software will accept molecular formulas and return compound names

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Manish replied | 28/06/2016

make its structure and derive thru iupac nomenclature

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Pratik 16/05/2016 in  IIT JEE Coaching classes

What do you call a compound that contains a metal and an acid anion?

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Gulab replied | 16/05/2016

Coordination Compound

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Shivendra replied | 16/05/2016

salt and hydrogen gas

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