What are Types of Solutions in Chemistry?

Solutions are homogeneous mixtures of two or more than two components. By homogeneous mixture it is meant that composition and properties are uniform throughout the mixture. Components of solution are called solute and solvent. Every solution is made up of a solvent and one or more solutes.

If water is the solvent, the solutions are called aqueous solutions and solutions in which other solvents like benzene, ether etc are used are called non-aqueous solutions. A solution containing one solute dissolved in a solvent is called a binary solution that is consisting of two components. Here each component may be solid, liquid or in gaseous state which is summarized in the table below.

Most chemical reactions are carried out in solutions. Body fluids are also solutions of various components in water. The most common types of solutions used in chemistry labs are solid-liquid, liquid-liquid and gas-liquid solutions. Thus a solution plays an integral part of lives.

What are Some Examples of Antiseptics?

Antiseptics also known as bacteriostatic agents inhibit the growth of germs but do not kill, microorganisms. Antiseptic generally applied to the skin or mucous membranes. Some also are used as cleansing agents. Some antiseptic such as iodine and hydrogen peroxide operate by oxidizing and thus destroying compounds essential to the normal functioning of bacteria.

Example of Antiseptic

Examples of Antiseptics

Some examples of antiseptics are given below:

• Soap – Some soaps contains small amounts of antiseptic substances which inhibits but not kill bacteria and fungi. The most frequent added antiseptic to soap are triclosan, triclocarbon, chloroxylenol. But usually soaps containing antiseptics are not recommended.

• Methylated spirits – Industrial methylated spirit is used as a rapid antiseptic in neonatal intensive care prior to invasive procedures such as venipuncture or lumbar punctures. It is also used with other antiseptics such as iodine or chlorohexidine.

• Hydrogen peroxide – Hydrogen peroxide has been commonly used as an antiseptic for all types of wounds as an adjunct to surgery, and as a treatment for chronic conditions. It is also used in the treatment of periodontal diseases and for root canal debridement during endodontic therapy.

• Dettol (a mixture of chloro xylenol and terpeneol in a suitable solvent) – Dettol was bactericidal against the wide range of microorganism tested, achieving a complete kill of the inoculum within 10min at dilutions in excess of the recommended use dilution.

• Tincture – Tincture is a renowned antiseptic against all internal and external infections. When tincture is used internally it promotes sweating and urination, so it may aggravate night sweats and hot flashes.

Acids, Bases and Salts

Many inorganic and organic compounds found in living organisms are ones that we use in our daily lives. They can be classified into one of three group’s acids, bases and salts. Almost all inorganic compounds and many organic compounds can be classified as acids, bases or salts. Acids and bases are strong chemicals and have opposite chemical properties. Acids have a sour taste while bases have bitter taste. When acids and bases react with each other, they form another class of compounds called salts.

Acids – Acids is a substance which produces hydrogen ions when dissolved in water. The word acid has been derived from a Latin word acidus which means sour. It is the hydrogen ions which makes the acid taste sour and turn blue litmus paper red. Hydrogen ions dissociate in aqueous solutions, so an acid will not show its characteristic properties unless water is present.

Bases – These compounds are chemically against acids. Bases have bitter taste. They are also called hydroxides as they have hydroxide group attached. Some bases are soluble in water, they are called alkalis. Alkalies turn red litmus paper blue. Antacid tablets contain magnesium hydroxide and carbonates which can neutralize the excess acid causing indigestion in our stomach.

Salts – Whenever an acid and base are brought together, water is always a product. A negative ion from the acid and a positive ion from a base are always left over. A salt is made up of a positively charged ion called a cation and a negatively charged ion called an anion.

Titration - To determine the Molarity of an Acid or Base

What Is Titration?

Titration is a procedure used in chemistry in order to determine the molarity of an acid or a base. A chemical reaction is set up between a known volume of a solution of unknown concentration and a known volume of a solution with a known concentration. The relative acidity (basicity) of an aqueous solution can be determined using the relative acid (base) equivalents. An acid equivalent is equal to one mole of H⁺ or H₃O⁺ ions. Similarly, a base equivalent is equal to one mole of OH- ions. Keep in mind, some acids and bases are polyprotic, meaning each mole of the acid or base is capable of releasing more than one acid or base equivalent. When the solution of known concentration and the solution of unknown concentration are reacted to the point where the number of acid equivalents equals the number of base equivalents (or vice versa), the equivalence point is reached. The equivalence point of a strong acid or a strong base will occur at pH 7.

For weak acids and bases, the equivalence point need not occur at pH 7. There will be several equivalence points for polyprotic acids and bases.

How to Estimate the Equivalence Point

There are two common methods of estimating the equivalence point:

1. Use a pH Meter

For this method, a graph is made plotting the pH of the solution as a function of the volume of added titrant.
    
2. Use an Indicator

This method relies on observing a color change in the solution. Indicators are weak organic acids or bases that are different colors in their dissociated and undissociated states. Continue reading..

How To Make Sulfuric Acid at Home?

Sulfuric acid is a useful acid to have on hand for a variety of home chemistry projects. However, it is not easy to obtain. Fortunately, you can make it yourself.

Homemade Sulfuric Acid Materials

Actually, this method starts with diluted sulfuric acid, which you boil to make concentrated sulfuric acid. This is the safest and easiest method of making sulfuric acid at home.

• car battery acid
• glass container
• outdoor source of heat, like a grill

Battery acid, which may be purchased at an automotive supply store, is approximately 35% sulfuric acid. In many cases, this will be strong enough for your activities, but if you need concentrated sulfuric acid, all you need to do is remove the water. The resulting acid will not be as pure as reagent-grade sulfuric acid, so keep this in mind.

Safest Method

If you aren't in a hurry, you can concentrate sulfuric acid by allowing the water to evaporate naturally. This takes several days.

1. Place an open container of sulfuric acid someplace with good circulation, safe from the possibility of a spill.
2. Loosely cover the container to minimize contamination with dust and other particulates. 
3. Wait. The water will evaporate out of the solution, eventually leaving you with concentrated sulfuric acid.

Note that sulfuric acid is highly hygroscopic, so it will retain a certain amount of water. You would need to heat the liquid to drive off the remaining water.

Quickest Method

 

The fastest method to concentrate sulfuric acid is to boil the water out of the acid. This is fast, but requires extreme care. You'll want to do this outdoors so that you won't be exposed to acid fumes, using borosilicate glass (e.g., Pyrex or Kimax). There is always a risk of shattering a glass container, no matter what you are heating, so you need to be prepared for that possibility. Do not leave this project unattended!

1. Heat the battery acid in a borosilicate glass pan.

2. When the liquid level stops dropping, you will have concentrated the acid as much as you can. At this point, the steam will be replaced by white vapor, too. Be careful to avoid inhaling the fumes. Continue reading..

Chemical Dynamics of Water Pollution

Chemistry has a long history – is it now time to turn our attention to repairing the damage chemical pollution has inflicted on the environment?

The origins of today’s scientific chemistry date to the turn of the 18th century from experimentation on water, combustion, medicine, and the study of heat.

With the experiments of Joseph Priestly, Antoine Lavoisier, Joseph Black, and Robert Boyle, modern-day chemists learned to understand the differences between alchemy and physical science.

Early Chemists

Although modern chemistry is a relatively new undertaking, the basis of chemistry lies within the origins of civilization. Although some recall the alchemists as early chemists, Alchemy originated from shamanic practices–inspiring their art with mysticism.

The first chemists were pragmatists–their discoveries came from necessity. The original science came from the hunter-gatherers who foraged for grubs, berries and discovered properties of the bark of the Willow tree (a source of primitive aspirin).

Other propitious discoveries included utilizing the foxglove plant for angina and the carrot for pigmentation. Moreover, several thousands of years later, primitive metallurgists utilized iron and bronze for plowing the earth and for weapons. Thus, between then and now, the science of chemistry grew to be appreciated and respected.

From soaps and diabetes medications to paints and gasoline, chemistry made our lives better and simpler.

The Dual-Edged Sword of Chemistry

Many lives have been saved, and riches have been amassed from the modern science of chemistry. However, many lives have also been ruined, and our world’s ecosystem is imperiled from a reckless use of chemistry.

Sadly, we have been poor stewards of the bigger picture. Every day, large volumes of chemicals pollute the  water. The sheer volume appears unimaginable, but it has initiated changes in the biosphere.

Organic chemicals include oil spills, agricultural runoff, and litter ranging from plastic bags to automobile tires.

Inorganic chemicals include litter, smoke and ash from coal-powered plants, and toxic metals (Cobalt, Arsenic, Antimony, Tin and Nickel).

This is the dual-edged sword of chemistry–it is a human aspect. Continue reading..

What is the Purpose of Chromatography?

Finding, isolating, and characterizing medicines derived from nature is a major sub-discipline within chemistry. One often-used technique for isolating potential medicinals is called chromatography – this is a process that separates similar molecules in a mixture.

Early methods separated molecules by color, so scientists called the process, ‘chromatography.’ How is this technique useful?

Chromatography Uses: Drugs From Food

An instance of a potential ‘drug’ isolated from food came from red wine in the 1990s. The substance known as resveratrol gained widespread acclaim as the possible ‘drug.’

Resveratrol was a part of the French paradox — how can people ingest rich, high calorie foods accompanied with a hearty Bordeaux or Pinot Noir wine without increasing their risk of a heart attack or stroke?

The paradox puzzled researchers, and identifying resveratrol as a preventative agent for heart disease was a stroke of scientific genius.

Resveratrol and chemically-similar compounds occur in wine grapes and are classified as phenolic stilbenes, substances which result from plant biochemistry. The eventual isolation of resveratrol via chromatography resulted in isolating other similar molecules of importance.

What are Phenolic Stilbenes–or Polyphenols?

The term stilbene originates from the german, stilbein~ to phosphoresce. The original discovery of the ‘stilbene class’ of molecules came in the late 1800s and was named as such because the molecule possessed a peculiar glow. Presently, theoreticians regard the molecule as rather mundane, except for the biochemical properties that were discovered in the mid-1990s. Continue reading..

How to Find Mass from Mole Fraction?

Mole fraction is simply the moles of a particular substance divided by the total number of moles present. Mole percent is mole fraction times 100. Similar to mole fraction, the mass fraction is nothing more than the mass of the substance divided by the total mass of all substances present. Although the mass fraction is what is intended to be expressed, ordinary usage employs the term mass fraction as well.

Mass (weight) fraction = mass (weight) of A / total mass (weight).

The term mass fraction and mole fraction are dimensionless. Mass percent is the amount of solute in grams present in 100g of the solution. Mole fraction is the ration of number of moles of a particular component to the total number of moles of the solution.

Let’s solve a problem based on mass and mole fraction.

Problem:

Consider 10mg of deprenyl is diluted in 10ml water. Water has the density of 1.0 g/ml. Calculate the mass fraction of the drug.

Solution:

To find the mass fraction first find the total mass of the solution, which is mass of water plus the mass of deprenyl.

m_{water} = (1.0g/mL) (10 mL) = 10g

Note that mass of the drug is negligible compared to the mass of water.

m_{total} = m_{water} + m_{drug} ~  m_{water}

The mass fraction of the drug is,

W_{drug} = m_{drug} / m_{water} = (10 mg/10g) (1g/1000mg) = 1.0 x 10^{-3}.

Examples of Endothermic Reactions

Endothermic reactions absorb heat energy from the surroundings. So that the temperature of the surroundings decreases. In endothermic reaction, the products formed are at a higher energy level than that of the reactants; hence energy is absorbed by the reactants from the surroundings.

Photosynthesis is an endothermic reaction.

 

In endothermic reactions, more energy is required to break bonds than is required to make bonds. Energy is absorbed and the surroundings get cooler. Sometimes you may see sportsman and women putting cold packs on injured ankles, knees or other parts of their bodies. One types of cold packs uses an endothermic reaction to work. The cold packs contains water and ammonium nitrate. As the ammonium nitrate dissolves in water an endothermic reaction takes place and the ice pack becomes very cold.

Some of the examples of endothermic reaction are given below:

1. Decomposition of compounds such as calcium carbonate, copper (II) carbonate, sodium nitrate etc.
2. Food being cooked.
3. Photosynthesis where green plants absorb light energy to make starch.
4. Dissolution of ionic salts like ammonium chloride, ammonium nitrate and sodium carbonate crystals in water.
5. Taking a photograph with a film, light energy is absorbed to decompose the silver bromide on the film to silver and bromine.

Endothermic reactions are less common than exothermic reaction, but there are a number which are quite familiar. For example, when certain salts such as potassium chloride and ammonium nitrate dissolve in water they take in heat from the surroundings and the temperature of the solution drops.
 

Subscripts and Superscripts in Chemistry

Subscript and superscript can make all the difference when it comes to chemical formulas.

Molecules, compounds, and other chemical structures include more than one atom. Sometimes, there are multiples of one particular atom. For instance, anhydrous aluminum chloride features one atom of aluminum joined to or combined with three atoms of chlorine. Its chemical formula reflects this: AlCl₃. But – simply knowing how to use a number in this instance is not enough. It is essential to know the proper use of subscripts and superscripts.

Subscripts in Chemistry

Notice the number 3 is written as a subscript, or a number that is smaller than the other text, and below the normal text line, in the formula for anhydrous aluminum chloride above. The concept of a multiplicity of atoms is conveyed by this use of a subscript.

You can also write the formula for Sucrose or table sugar, using chemical symbols and subscript numbers. There are 12 carbon atoms, 22 hydrogen atoms, and 11 oxygen atoms in sucrose – the chemical formula for table sugar looks like this: C₁₂H₂₂O₁₁.

Sometimes parentheses are used to characterize a particular structure, as follows: (CH₃)₃CCOOH

The above molecule is pivalic acid. We occasionally refer to this molecule as trimethylacetic acid, since, visually, the molecule contains 3 methyl groups CH_3-. Written in its most elemental form, the formula for pivalic acid is C₅H₁₀O₂.

Another more complex structure – acetone, or dimethyl ketone – exemplifies the beneficial use of parentheses.

CH₃(CO)CH₃

How are the parentheses beneficial? In this instance, it is because the oxygen atom is not connected to either the leftmost or the rightmost carbon atom but only the middle carbon atom. Acetone’s chemical structure could also be written (CH₃)₂CO or (CH₃)₂C=O.

 

Superscripts in Chemistry

Atoms often occur as combinations of isotopes. Hydrogen, the simplest gaseous element, has one electron and one proton in all its atoms. However, a small percentage of hydrogen atoms also have a neutron in the nucleus. This form of hydrogen atom is, naturally, heavier than the hydrogen without a neutron. To distinguish them, a superscript is employed. The letter H with a left-justified superscript symbol 1, written ¹H, represents hydrogen containing one nucleon – that is one nuclear particle – a lone proton. Continue reading..

Hydrogenation of Benzene

Benzene hydrogenation is a major petrochemical process. Benzene is readily hydrogenated to cyclohexane using nickel or platinum in fixed beds. Most of the cyclohexane nearly 98% is produced by benzene hydrogenation process. Generally this reaction is carried out at 160 – 220$^{\circ}$C and 25 – 30 atm. Many catalyst such as Ni/alumina and Ni/Pd are used for the reaction.

Benzene hydrogenation has been chosen as a model aromatic substance. This reaction has also been used as model reaction in heterogeneous catalysis by metals where metal-support interactions are involved and the desired product of benzene hydrogenation – cyclohexane is an important chemical intermediate for the synthesis of nylon-66 and nylon-6.

During hydrogenation of benzene some two important observations are made.

1. Partially hydrogenated benzene derivatives were never found – only reaction ends in the formation of cyclohexane.
2. Cyclohexane was dehydrogenated above 200^oC to give the reverse reaction. At higher temperatures benzene cracked to form methane and carbon.

Benzene must be free from sulfur to avoid poisoning the catalyst although the original short uneconomical catalyst were common. Reaction temperature and exotherm can be controlled by evaporation of the product and dilution of the benzene feed with recycled cyclohexane.