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Chemistry Interview Questions and Answers


This page contains the collection of Chemistry Interview Questions and Answers / Frequently Asked Questions (FAQs) under category Science. These questions are collected from various resources like informative websites, forums, blogs, discussion boards including MSDN and Wikipedia. These listed questions can surely help in preparing for Chemistry interview or job.

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What is an oxidizing agent?
Any chemical species that has a tendency to accept electrons and thereby undergoing reduction themselves is known as an oxidizing agent

What is the dipole moment of chlorooctane?
There are multiple forms of the molecule "chlorooctane." This is because the chlorine atom can be attached to the octane chain in several different places, and each different placement will result in a different dipole moment. If you specify the structure of the compound more precisely (1-chlorooctane or 2-chlorooctane for example), it is possible to determine its dipole moment.

How do you extract ephedrine from a mineral block?
You cannot extract ephedrine or pseudo ephedrine from a mineral block. Anyone who tells you that they have done it is either mistaken or a liar.

What are the hydrocarbons?
Hydrocarbons are compounds made entirely out of Hydrogen and Carbon.

How do you prepare a solution of 1 M HCl?
Exactly how you prepare will depend on what you are starting with. Typically, to make a 1 M HCl solution, you will be starting with a stock solution of more concentrated HCl that you will then dilute.

What are KOH and HCl?
KOH is potassium hydroxide, which is a strong base. HCl is hydrochloric acid, which is a strong acid.

Is DNA organic?
► Of, relating to, or derived from living organisms: organic matter.
► Of, relating to, or affecting a bodily organ: an organic disease.

In addition, DNA would chemically be considered organic since it contains carbon as the primary chemical backbone of the molecule.

What is hydra?
Hydra is a type of polyp. It is an animal, because it moves around like one even though it looks like a plant. A hydra is from the Phylum Cnidarian and belongs with others such as jellyfish and coral.

What is alum?
Alum is a chemical (aluminum potassium sulphate); it tends to be whitish powder with several uses, including:

1. As an astringent
2. As an antibacterial
3. As a food preservative
4. As a 'Styptic pencil' to heal shaving cuts
5. To stem the flow of minor blood loss and cuts
6. Soaked into materials to make them flame retardant

There are other uses, but these are some of the more common ones.

What is the difference between the law of multiple proportions and the law of definite proportions?
Both laws have to do with relating to Dalton's Atomic Theory. The only difference is that the Law of Definite Proportions deals with elements combining to form ONE compound in a simple whole number ratio. The Law of Multiple Proportions is comparing the same 2 elements that make up 2 different compounds the division of these 2 ratios should equal a simple whole number ratio.

For example, Carbon and oxygen can combine to form carbon monoxide and carbon dioxide. If you calculated each compounds ration of oxygen to carbon, you would get the following ratios: compound A would equal a combining ratio of 1.34:1 (O:C). Compound B would equal a combining ratio of 2.67:1 (O:C).

If you divided the bigger ratio by the smaller ratio you would have that oxygen combines with a ratio of 2.67/1.34, which would equal 1.99:1, which is close enough to 2:1.

What is the structure of a DNA molecule?
A molecule of DNA is double-stranded. The molecule has the shape of a double helix.

The DNA molecule consists of two complementary strands oriented in an anti-parallel fashion. Each strand is composed of nucleotides. A nucleotide consists of a base (a purine or pyrimidine), a sugar (between the other two components) named deoxyribose, and a phosphate group. Nucleotides are linked to each other via phosphodiester bonds, forming a sugar-phosphate backbone to each strand.

The base of each nucleotide projects into the interior cavity of the helix. Each base is opposite another base: adenine (a purine) is always paired with thymine (a pyrimidine), and guanine (purine) with cytosine (pyrimidine); this phenomenon is called complementary base pairing.

Each nucleotide forms hydrogen bonds with its complementary base on the other strand. Two hydrogen bonds form between adenine and thymine; three hydrogen bonds form between guanine and cytosine.

What is a medicine dropper?
A medicine dropper is an instrument used to measure small amount of liquids, usually in milligrams. You will first pinch the handle before you submerge it in the water.

How many electrons are in benzene?
There are 30 electrons in benzene. This includes 24 carbon electrons and 6 hydrogen electrons. There are 12 electrons shared between C and H, and 18 between C and C. (6 electrons in up ring, 6 in down ring and 6 between C and C).

What is a dipole moment?
Dipole moment is the measure polarity of a polar covalent bond. It is defined as the product magnitude of charge on the atoms and the distance between the two bonded atoms. Its common unit is debye and SI unit is columb meter.

Where is tin obtained?
Tin is obtained in various places tin is found mainly in the ore cassiterite, which is found in Malaysia, Bolivia, Thailand, and Nigeria.

What are the differences between organic and inorganic chemistry?
Organic chemistry is the chemistry of carbon compounds while inorganic chemistry is the chemistry of all the rest of the elements on the periodic table.

How reactive is Trimethylindium towards oxygen and water?
Trimethylindium is extremely reactive towards oxygen and water. With low concentrations of oxygen (ppb to ppm to a few %), it immediately forms dimethylindium methoxide (Me2InOMe) as the first reaction product by insertion of O between In and C. With increased concentrations of oxygen (several %, atmospheric air or pure oxygen), it burns or explodes. Similar insertion reactions are expected with other elements of Group 16 (such as S, Se and Te) with highly vigorous outburst at higher concentrations of S, Se and Te.

Trimethylindium reacts readily and vigorously with water to form Me2InOH and Methane (CH4) gas if the concentration of H2O is very small (up to 1000's ppm). With high concentrations of water (% level), trimethylindium can burn and often explode leaving behind In (OH)3, In2O3 as the final products. Extremely violent reactions of trimethylindium are also known with oxidizers. Such as H2O2, KMnO4, HNO3, Bleach) and halogenated compounds (CCl4, CBrCl3, CBr2Cl2, CHCl3, C2Cl6, and halocarbon oils).

What are the cons of eating organic foods?
It is more expensive and you have less of a variety to choose. Stores like Wegamans have a variety of organic food though.

Since organic produce does not contain chemicals and stabilizers, it spoils more quickly. It also may appear "uglier" (asymmetrical, not shiny or waxy, dirty).

How many moles of HCl are present in .70 L of a .33 M HCl solution?
► First, remember definition of M (moles), M = moles of species / L.

0.33 M = 0.33 moles HCl / L

► Then, multiple your volume by the molar concentration:

0.33 moles HCl / L x 0.70 L = 0.231 moles HCl

It is helpful to carry the units with your calculations. That way you can check that numerators and denominators cancel to give you the units of your answer.

What is the equation for photosynthesis?
1) Light energy

2) == 6CO2 + 6H2O --------> C6H12O6 + 6O2 ==

3) Carbon dioxide + water +light energy------> carbohydrates+ oxygen

What is a tripod? How it is used?
A tripod is a general term for a stand or support with three legs. It is often used to support a camera gun, or to place above the Bunsen burner in the science lab to heat/boil anything.

In the science laboratory, metal gauze is placed on top of it to give support to the beaker (An iron ring clamp with a ring stand can often be used instead and an iron ring allows for easy height adjustment).

What is ciprofloxacin HCL used for what type?
Ciprofloxacin is used to fight bacterial infections. I am currently taking this medicine to help cure mastoiditis.

What is protein in Chemistry?
Protein is a source of backup energy that your body stores, a large complex molecule made up of one or more chains of amino acids. Proteins perform a wide variety of activities in the cell.

Highly complex nitrogenous compounds found in all animal and vegetable tissues. Proteins, the principal constituents of the protoplasm of all cells (apart from water), are of high molecular weight, and consist essentially of combinations of amino acids in peptide linkages. Twenty different amino acids are commonly found in proteins and each protein has a unique, genetically defined amino acid sequence that determines its specific shape and function.

Where does arsenic come from?
(FeAsS) Arsenopyrite also known as mispickel is the most common mineral containing arsenic.

Do all explosions produce carbon dioxide?
An explosion is nothing more than the rapid release of energy. This is most commonly due to the rapid combustion of a material, although nuclear explosions do not involve combustion. The combustion of any hydrocarbon or other carbon-containing substance ALWAYS produces carbon dioxide. This might include explosion due to a natural gas or gasoline.

It is possible, however, to explode substances that do not contain carbon, such as pure hydrogen (the very famous Hindenburg disaster in 1937 is a classic example of a very big hydrogen gas explosion. An explosion of hydrogen produces only water vapor (H2O), NOT carbon dioxide (CO2).

Also, nuclear explosions (both fusion and fission) themselves do not produce carbon dioxide, although they may cause surrounding objects to incinerate, which would release carbon dioxide.

What is the octet rule in chemistry?
The octet rule is a simple chemical rule of thumb that states that atoms tend to combine in such a way that they each have eight electrons in their valence shells, giving them the same electronic configuration as a noble gas. This 8-electron configuration is especially stable because with 8 valence electrons, the s- and p-orbitals are completely filled (with 2 in the s-orbital, and 6 in the p-orbitals). Having completely filled orbitals provides increased stability due to something called "exchange energy."

The rule is applicable to the main-group elements, especially carbon, nitrogen, oxygen, and the halogens, but also the metals in the first two columns of the periodic table (but not to the transition metals in the middle of the periodic table). Note that the elements hydrogen (H) and helium (He) do not follow the octet rule, but rather the "duet" rule (2 electrons) because they do not have any p-orbital electrons.

In simple terms, molecules or ions tend to be most stable when the outermost electron shells of their constituent atoms contain eight electrons. The rule is commonly used in drawing Lewis dot structures.

Why chemists have not created a periodic table of compounds?
One major reason I can think of, that has not been addressed yet, is the periodicity of the elements. You can line the elements up into neat functional groups--alkali metals, transition elements, halogens and so on. This you could not do with compounds, even if you had a separate table for hydrocarbons, one for elastomers, and one for dyestuffs... Compounds also find wide use as smaller blocks of larger compounds. We call these precursors. Take toluene. It is a very toxic compound, but if you compound it into toluene diisocyanate, then compound that into polyurethane, it becomes safe enough that you can build it into replacement hip joints. Chemists do keep books of compounds, but a table on a big sheet of paper the size of...oh, the entire side of a Wal-Mart store might be big enough? It could never happen.

How do you solve Ideal Gas Law problems?
The Ideal Gas Law is used to relate the pressure, volume, temperature, and amount of an "ideal" gas. Although many gases are not ideal in reality, you can usually use the Ideal Gas Law anyway. Here is how you solve these problems!

The Ideal Gas Law is PV = nRT.

What is the direction of the dipole moment expected for hydrogen bromide?
The HBr molecule is linear (obviously, since it contains only two atoms). The dipole moment is a vector, parallel to the bond, pointing toward the partially positively charged atom, which is, in this case, the hydrogen. The magnitude of the dipole moment is the difference in the partial electrical charges on each atom times the spatial separation of the atoms in the bond. In a molecule with more than two atoms (more than one bond), the dipole moment of each bond must be added vectorially and the resultant vector will determine the dipole moment of the molecule. For instance, carbon dioxide has two carbon-oxygen double bonds of high polarity, but because the molecule is linear, and the individual dipoles oppose each other, the carbon dioxide molecule has no net dipole moment.

What is a substituted hydrocarbon?
A substituted hydrocarbon is a hydrocarbon with one or more of the hydrogen is substituted with another element, (often a halogen such as chlorine or bromine) or another group of atoms such as -OH. Examples: -

a simple hydrocarbon is methane CH4. Substitute chlorine for hydrogen to get

CH3Cl Methyl Chloride is used for cleaning. Sub. Again to get

CH2Cl2 Methylene Chloride is used as paint stripper. Sub again to get

CHCl3 Chloroform is an ancient anesthetic. Sub again to get

CCl4 Carbon Tetrachloride is used in cleaning and fire extinguishers.

Substitute a single -OH group into -

CH4 to get CH3OH methanol or into C2H6 to get C2H5OH ethanol

The above examples all begin with unbranched non-cyclic hydrocarbons, but any hydrocarbon is a suitable target. A well-known instance is a double substitution of chlorine at opposite ends of a benzene ring to form paradichlorbenzene, commonly found hanging in toilet bowls. C6H6 becomes C6H4Cl2

What is the net charge of a non-ionized atom?
In an atom, the number of protons is equal to the number of electrons and that one proton has the same positive charge value as an electron does a negative charge value.

Therefore, I am assuming that all atoms have no charge, zero, none, squat.

Non-ionized also means the atom has not suffered electron exchange, so a non-ionized atom is really just an atom (which is word redundancy).

This is what I know from AS level Chemistry, so I don't know if it's the same thing as more advanced chemistry (for university or something).

Why acetic has less conductivity than Hcl?
Acetic acid has less conductivity, because it ionizes less in solution. HCl separates almost completely in solution to form the ions Cl- and H+. Acetic acid only partially ionizes into CH3COO- and H+ with lots of it staying as complete CH3COOH molecules. It is the concentration of ions in a solution, which determines its conductivity. An electric current passes through the solution by movement of these ions. The extent to which any partially ionized substance actually ionizes can be expressed as its pKa value.

What is the chemical formula of detergent?
The chemical formula for detergent certainly is not "c3h8o5," as was suggested. ("c3h8o5" does not even exist as a molecule.)

Rather, the chemical formula for "detergent" really depends on what you mean by the word. By itself the word does not connoted any specific formula (must/must not have this function group).

Commercial detergents are made up of many different chemical compounds (different surfactants, colorants, pH modifiers, chlorinated and non-chlorinated whiteners, etc). For example, one effective (albeit harsh) surfactant is sodium lauryl sulfate (aka sodium dodecyl sulfate): C12H25NaO4S.

How can you tell if there is a dipole moment or not?
A dipole moment is defined as a measure of the molecular polarity of a compound; the magnitude of the partial charges on the ends of a molecule times the distance between them (in meters).

In order for there to be a dipole moment, the element must have molecular polarity, which results from molecules with a net imbalance of charge (often a result of differences in electro negativity). If the molecule has more than two atoms, both shape and bond polarity determines the molecular polarity.

In general, look for a difference in electro negativity of the elements of a molecule which results in polarity and thus a possible dipole moment. Note that molecular shape influence polarity so molecules with the same elements but a different shape (and vice versa) will not have the same dipole moment.

Is benzene a polar molecule?
No, Benzene is a non-polar compound

Is HCl an acid or a base?
HCl, or hydrochloric acid, as the name implies, is an acid. In fact, it is considered a strong acid because it dissociates completely in water to form H3O+ and Cl-.

However, it can also act as a base in reactions with acids stronger than it can like HClO4.

What is the IUPAC name of benzene?
The IUPAC name for Benzene is Benzene. It forms the basis for other IUPAC-named benzene derivatives like 1, 2-dimethylbenzene etc.

What wavelengths can the human eye see?
Human eye is sensitive to an approximate range of wavelength of radiations from 380nm to 760nm. This portion of electromagnetic spectrum is identified as Light

What makes a molecule into an organic molecule?
Any molecule that contains one or more atoms of Carbon is an organic molecule. All elements that are composed by Carbon are studied by Organic Chemistry.

How are dipole attractions London dispersion forces and hydrogen bonding similar?
They are all forces of attraction used to kelp keep molecules together. Since the molecules are the atoms bonded together, there are no electrons, or not enough, left over to bond with more atoms. The result would be trillions of tiny molecules floating about. Instead, each of these types of attractions draws the molecules together into solids, liquids, or gases.

Which is polar HCl or HF?
This question is quite simple if you have an electro negativity chart:

Florine's Electronegativity: 4.0

Chlorine's Electronegativity: 3.0

Hydrogen's Electronegativity: 2.1

HCl: 3.0-2.1= .9 (Slightly polar)

HF: 4.0-2.1= 1.9 (Much more polar)

How does spontaneous combustion occur?
It is caused by a build up of sulfur in a person's body that eventually reacts to increased body heat.

What is the use of glacial acetic acid?
There are no medical uses to pure GAA, dilute concentrations can be used to remove warts or verucas; it can also be used via iontophoresis to treat bone spurs. Industrial uses include photography and the manufacturing of aspirin.

How do you separate the colors of ink?
The colors of ink can be separated by chromatography.

What is some importance of organic chemistry?
In organic chemistry one uses it both medicinally one uses it to test for illness way back from ancient times. It is also a good diagnostic tool by smell feel or touch. You can actually heed the smell of decay in organic chemistry

What are 3 facts on evaporation?
1. 80% of evaporation comes from the ocean.
2. 20% of evaporation comes from inland water.
3. Wind helps evaporation by moving it

Explain the method for the preparation of 1 normal solution of hydrochloric acid.
Dilute 85ml of HCL to 1000ml

Can you show you the organic structure of cetearyl alcohol and tell me what organic family it is?
Cetearyl alcohol is actually a mixture of both stearyl alcohol and cetyl alcohol (refer to links below for structures). Both of these compounds would be considered "fatty alcohols" due to their long carbon chains. Fatty alcohols are in the aliphatic hydrocarbon family. To draw the structure of "cetearyl alcohol" you would actually have to draw the structure of cetyl alcohol and the structure of stearyl alcohol.

Are the chemical properties of lithium a metal metalloid or a nonmetal?
Lithium, Li, is a metal. However, can also be a metalloid or a nonmetal.

What is the chemical formula for Epsom salts?
Epsom Salt chemical formula is Me245-H2O.

Is benzene an element or a compound?
Benzene is a compound.

What is the full form of hcl?
The full form of HCL is hydrochloric acid or hydrogen chloride gas

What is the direction of the dipole moment expected for carbon tetrachloride?
It has no net dipole moment. Hence, it is non-polar.

What is the difference in the modern periodic table and Mendeleevs table?
The periodic table is now arranged in the order of increasing atomic numbers. In addition, it is said that the modern table makes it easier to read and learn. The way that it is set up now allows scientists to make changes if necessary. Hope this helps

What element was used to make the first atomic bomb?
Uranium was used in the Hiroshima bomb and Plutonium in the Nagasaki one.

How do you convert oxygen gas to liquid oxygen?
Condense in a temperature less than -186 c ideally with liquid helium or other cryogenic means.

Is HCl polar or non-polar?
Yes, HCl is a polar compound because chlorine is more electronegative than H It attract the bond pair towards itself. Hence, compound is a polar.

What is the chemical formula for dichromate?
Dichromate is Cr2O7.

What is the Ionic equation for HCL-NaOH?
H+ + OH- -> H20

What are some examples of a reversible reaction?
1. Conversion of ammonium cyanate into urea
2. Dissociation of hydrogen iodide
3. Reaction between gaseous CO and NO2

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