Formula and Equation writing

The ability to write formula and balance equations is an essential skill in chemistry and forms the starting point for solving most problems.

Writing Formula

Chemical compounds typically consist of one or two endings; -ide and -ate with the exception of hydroxides, a compound ending -ide will be made up of just two elements and those ending -ate will also contain the element oxygen (eg magnesium sulfate, MgSO4)

Chemical name often give an indication as to the formula of a compound. A good example of this is carbon dioxide (CO2). These prefixes can be used to quickly write a formula.Where a formula is not obvious, a system of combining powers can be used to work out the most likely ratio of elements. It begins by assigning combining powers to the columns in the periodic table.Transition metals (elements in the middle of the table) are able to show a variety of combining powers and such have Roman numerals that show the combining power (oxidation number) involved. For example the combining power of cobalt in cobalt IV chloride is 4, but 2 in cobalt II iodide.

Compound or polyatomic ions are groups of atoms that are covalently bonded but have an overall change. These species can also be assigned combining powers based on their charges. Some will become more familiar once the chemistry of acids has been studied.Having identified the elements involved and their combining powers, a crossing over rule can be used to construct the formula. In this method the powers are switched and if a common factor exists then the ratio of elements is cancelled down. Brackets are used, as in maths, for multiple groups of compound ions. For example, in magnesium hydroxide, Mg(OH)2, there are two hydroxide ions for every one magnesium ion.Balancing equations

Balanced equations show how chemicals react to form new products and contain the same number of each type of atom on both sides of the equation. Only whole numbers (coefficients) can be added to the front of formula to achieve this. It is also worth remembering that seven of the elements exist in their natural, uncombined forms as diatomic molecules (H2, O2, N2, F2, Cl2, Br2, I2).

An example of the steps used to balance an equation is shown below fir the reaction between iron and oxygen to form iron III oxide.

Step 1 Write in the symbols for the chemicals. Use combining powers where necessary. Looking at the equation it is apparent that the numbers of each type of atom on each side of the equation are not the same – it needs balancing.

Fe + O2 —-> Fe2O3

Step 2. The odd number of oxyge atoms on the right hand side of the equation and even number of the left will make balancing tricky. Address that problem first.

Fe + O2 —-> 2Fe2O3

Step 3. Now balance the Fe atoms

4Fe + O2 —->2Fe2O3

Step 4. And finally the O atoms.

4Fe + 3O2 —–> 2Fe2O3

State symbol should be included in balanced equations whenever possible. These letters in brackets indicate whether a chemical is solid (s), liquid (l), gas (g) or dissolved in water (aq). For the example above the equation then becomes.

4Fe(s) + 3O2(g) —–> 2 Fe2O3(s)

How to Study Organic Chemistry?

Organic Chemistry is a challenging subject. It uses its own language and employs many very precise concepts yet without referring mathematical tools or aspects. Within first few hours of study you will be able to use the basic concepts to understand a lot about the molecular world around you.

The first difficulty a student encounters is the amount of study material available about organic molecules and their reactions any standard text book is not less then 1400 pages long, a student cannot expect to learn all this material without investing a considerable time and effort in studying it and if he does so he disproportionate his time allocations with other subjects eventually bringing him under pressure to leave organic chemistry or compromise at other subjects.

The solution of above problem is that someone should work on your part to extract all relevant important matter and concept for you, this someone is your teacher. Most of standard text book (like I L Finar Morison boyd) available in market are not oriented for JEE preparation, rather these are among the best books available for college students all over the world. The sequence of chapters or 100% content may not return you for the time you have invested. You need not follow line to line of the text but choose the desired component from the word index given at the back of book.

Why study Inorganic Chemistry?

About 1 in 10 professional chemists is an inorganic chemist, but all chemists and many other scientists must work with inorganic compounds: in the laboratory, in the field or in theory.

Among chemists, organic chemists have always relied on inorganic reagents to carry out syntheses; this trend is increasing as organic synthesis turns more and more to the use of specific transition metal catalysts and nonmetallic compounds. Analytical chemists are often concerned with the detection and quantification of elements other than carbon, and often use chelating ligands of appropriate hardness or softness to concentrate and detect metallic elements. Physical and theoretical chemists are concerned with measuring or calculating the fundamental properties of inorganic and organic substances. Modern biochemists are becoming increasingly aware of the critical role played in living systems by metal ions. In addition there are many times when any chemist must make up a solution of a new type of inorganic reagent, modify a synthesis, detect an element in a new form, or study the properties of a different type of inorganic compound. At this point, the chemist needs to have some ability to anticipate the properties of inorganic compounds he or she has not dealt with in the past.

Chemistry and Measurement

All of the objects around you – your pen or pencil, and the things of nature such as rocks, water, and plants and animal substances – constitute the matter of the universe. Each of the particular kinds of matter, such as a certain kind of paper or plastic or metal, is referred to as a material. We can define chemistry as the science of the composition and structure of materials and of the changes that materials undergo.

One chemist may hope that by understanding certain materials, he or she will be able to find a cure for a disease or a solution for as environmental ill. Another chemist may simply want to understand a phenomenon. Because chemistry deals with  all materials, it is a subject of enormous breadth. It would be difficult to exaggerate the influence of chemistry on modern science and technology or on our ideas about our planet and the universe. In the section that follows, we will take a brief glimpse at modern chemistry and see some of the ways it has influenced technology, science, and modern thought.

Modern Chemistry: A brief Glimpse

For thousands of years, human being have fashioned natural materials into useful products. Modern chemistry certainly has its roots in the endeavor. After the discovery of fire, people begun to notice changes in certain rocks and minerals exposed to high temperatures. From these observations came the development of ceramics, glass, and metals, which today are among our most useful materials. Dyes and medicines were other early products obtained from natural substances. For example, the ancient.

Laboratory notebook format

Use the following general format for recording an experiment in your lab notebook:

Introduction

The following information should be entered before you begin the laboratory session:

Date
Enter the date at the top of the page. Use an ambiguous date format, such as 2 September 2008 or September 2, 2008 rather than 2/9/8 or 9/2/8. If the experiment runs more than one day, enter the starting date here and the new date in the procedure/data section at the time you actually begin work on that date.

Experiment title
If the experiment is from this or another laboratory manual, use the name from that manual and credit the manual appropriately. For example, “Quantitative Analysis of Chlorine Bleach by Redox Titration (illustrated Guide to Home Chemistry Experiments, #20.2)” If the experiment is your own, give it a description title.

Purpose
Write one or two sentences that describe the goal of the experiment. For example, “To determine the concentration of chlorine laundry bleach by redox titration using a starch-iodine indicator.”

Introduction (optional)
Any preliminary notes, comments, or other information may be entered in a paragraph or two here. For example, if you decided to do this experiment to learn more about something you discovered in another experiment, not that fact here.

Balanced equations
Write down balanced equations for all of the reactions involved in the experiment, including if applicable, changes in oxidation state.

Chemical information
Important information about all chemicals used in the experiment, including, if appropriate, physical properties (melting/boiling points, density, etc.), a list of relevant hazards and safety measures from the MSDS (the Material Safety Data Sheet for the chemical), and any special disposal methods required. Include approximate quantities, both in grams and in moles, to give an idea of the scale of the experiment.

Planned procedure
A paragraph or two to describe the procedures you expect to follow.

Main body

The following information should be entered as you actually do the experiment:

Maintaining a laboratory notebook

Laboratory notebook

Laboratory notebook

A laboratory notebook is a contemporaneous, permanent primary record of the owner’s laboratory work. In real-world corporate and industrial chemistry labs, the lab notebook is often a critically important document for both scientific and legal reasons. The outcome of zillion-dollar patent lawsuits often hinges on the quality, completeness, and credibility of a lab notebook. Many corporations have detailed procedures that must be followed in maintaining and archiving lab notebooks, and some go so far as to have the individual pages of researcher’s lab notebooks notarized and imaged on a daily or weekly basis.

If you’re just starting to learn about chemistry lab work, keeping a detailed lab notebook may seem to be overskill, but it’s not. If you plan to take the Advanced Placement (AP) Chemistry exam, you should keep a lab notebook. Even if you score a 5 on the AP Chemistry exam, many college and university chemistry departments will not offer you advanced placement unless you can show them a lab notebook that meets their standards.

Laboratory notebook guidelines

Don’t do stupid things

Home Chemistry Laboratory

Home Chemistry Laboratory

This a list of strictly NOT TO DO STUPID THINGS in a chemistry laboratory:

Never eat, drink or smoke in the laboratory
All laboratory chemicals should be considered toxic by ingestion, and the best way to avoid ingesting chemicals is to keep your mouth closed. Eating or drinking (even water) in the lab is very risky behavior. A moment’s inattention can have tragic results. Smoking violates two major lab safety rules: putting anything in your mouth is a major no-no, as is carrying an open flame around the lab.

Never work alone in the laboratory
No one adult, or tutor or student, should ever work alone in the laboratory. Even if the experimenter is adult, there must at least be another adult within earshot who is able to respond quickly in an emergency.

No horsing around
A lab isn’t the place for practical jokes or acting out, or for that matter for catching up on gossip or talking about last night’s football game. When you’re in the lab, you should have your mind on lab work, period.

Never combine chemicals arbitrarily
Combining chemicals arbitrarily is among the most frequent causes of serious accidents in home chemistry labs. Some people seem compelled to mix chemicals more or less randomly, just to see what happens. Sometimes they get more than they bargained for.

Classification of Matter

Classification of matter according to Chemistry

Classification of matter according to Chemistry

When a person is confronted with a large number of objects or ideas, it is only natural to want to classify and organize them into groups. The advantage of grouping items is that you will end up with a smaller number of groups than objects. In your day-to-day life, you may group baseball cards according to teams or positions. You may organize your books according to titles or authors. At the very least, you probably have a sock drawer. Do you organize your clothes into drawers, according to the type of item? This allows you to remember where you keep your shirts, rather than memorizing where a specific shirt may have been placed.

A good classification scheme will allow you to memorize the characteristics of the groups, which you can then apply to all of the objects in the groups. In other words, rather than memorizing the characteristics of millions of organisms, a biologist will memorize the characteristics of different kingdoms. If an organism is known to belong to a certain kingdom, then the biologist will know some of the characteristics of the organism, based on the known characteristics of the kingdom.

It is important to realize that these classification schemes are manmade, which means that we make up the categories and classes. The classification schemes can change, if someone comes up with a system that scientists like better than the present system. The present classification scheme for chemistry will probably seem very simple and elegant to you, especially if you have recently studied the classification system of biology.

As you can see in the above graphic, all matter can be divided up into four main categories. Of course, there are other ways to classify matter, but this system is the one that seems to be generally recognized right now. Although the diagram is concise, it may not be completely clear unless we read about all of the categories in more detail. Once you understand the categories, the chart should be all that you need to review.

Chemistry Experiment: Separating a sand and salt mixture

Topic
Separation techniques

Timing
45 minutes

Description
In this experiment students use simple processes to separate sand and salt.

Apparatus and equipment (per group)

  1. 250 cm(3) Beaker
  2. Filter funnel and paper
  3. Evaporating dish
  4. Tripod
  5. Bunsen burner
  6. Gauze
  7. Glass rod for stirring

Chemicals (per group)
A mixture of salt and sand (about 20 percent of salt)

Teaching tips
It can be effective to show the separate sand and salt to the whole class. Mix them at the front of the class, then use this as an introduction to a class discussion about how to separate them.

Background theory
The principles of filtration, evaporation, and the dissolving process.

Answers

To dissolve the salt in water.
The sand is filtered out into the filter paper; the filtrate is salt solution.
To remove the majority of the water.

Introduction
In this experiment simple processes are used to separate salt from a sand and salt mixture.

What to do

  1. Mix about 5g of the mixture with 50 cm(3) of water in a 250 cm(3) beaker. Stir gently.
  2. Filter the mixture into a conical flask and pour the filtrate into an evaporating basin.
  3. Heat the salt solution gently until it starts to ‘split’. Care: do not get too close.
  4. Turn off the Bunsen burner and let the damp salt dry.

Safety
Wear eye protection.

Questions
Why is the salt, sand and water mixture stirred in step 1?
What happens when this mixture is filtered in the step 2?
Why is the salt heated in step 3?

Setting up your laboratory

Chemistry home laboratory

Chemistry home laboratory

In some ways, a laboratory is very much like a library; but instead of looking up information, the laboratory worker find out about it for himself. In both places the working conditions are similar. Librarians must catalog books in a library and store them in a neat and orderly fashion. Chemists must label their equipment and chemicals in a laboratory and store them in an equally neat and orderly manner. Silence in a library is essential, so the people using it can concentrate on their work. Chemistry tutors say silence is essential in a laboratory too, so the workers can give their complete attention to their work.

For these reasons, and also for the sake of safety and convenience, you will want to find some special place at home in which to establish your laboratory. It must be reasonably quiet and out of everyone else’s way. It must be well lighted and there must be a sink in the laboratory, or very close by, so you can easily get water. To be completely on the safe side, it should be in a place that the younger children can’t get to easily. Your fascinating collection of apparatus and chemicals may tempt them to try things that might prove dangerous.

Once you have chosen a good location you will need these things:

  1. A large table on which to perform your experiments. You should cover it with a heat- or chemical-proof substance, such as linoleum, glass or tile. If this is not possible, several layers of newspaper, which you must change regularly will do.
  2. Above your work area, there should be one or two shelves on which to keep your chemicals – all, of course, properly labeled and stored, either alphabetically or in groups according to the type of experiment in which you may use them. There is one important exception to this, however. Do not place an acid, such as vinegar, near an alkali, such as ammonia. Enough molecules of each substance can escape even from closed bottles to cause a chemical reaction in the surrounding air. The reaction could contaminate the outside of the bottles and the chemicals nearby.
  3. Your laboratory apparatus will include those items which you can make yourself, a few things you will have to purchase, plus many things you can collect, such as baby-food jars, small plastic bottles and corks of different sizes. Keep all of these in separate places on the shelves, or in drawers or boxes which are clearly labeled.
  4. Be sure to have at least one ceramic or pottery waste container for discarded, used, or unwanted solid chemicals, for broken glass, and for the remains of successful experiments. To get rid of liquid wastes, you must pour them into a sink, with the water constantly running, or put them into a separate metal waste container.
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