Tag Archives: chemistry

Calculate Theoretical Yield of a Chemical Reaction – Theoretical Yield Example Problem

Gas Collection Woodcut

Source: Elements of Modern Chemistry, Charles Adolphe Wurtz, 1887.

The theoretical yield of a chemical reaction is the amount of product you expect to get after a chemical reaction takes place from the reagents you have available. To calculate the theoretical yield of a reaction, you must first know the reaction. Let’s look at the following reaction where heating potassium chlorate (KClO3) produces oxygen gas (O2).

2 KClO3 (s) → 3 O2 (g) + 2 KCl (s)

where KCl is potassium chloride. This reaction is fairly common in school laboratories since it is a relatively inexpensive method of obtaining oxygen gas.

The balanced reaction shows that 2 moles of KClO3 will produce 3 moles of O2 and 2 moles of KCl. To calculate the theoretical yield, you use these ratios as a conversion factor.  Here is a typical example problem.

Calculate Theoretical Yield Example Problem

Question: How many moles of oxygen gas will be produced from heating 735.3 grams of KClO3?

Answer:

Step 1. We need to know the amount of KClO3 in moles to use the conversion, so the first step is to convert grams KClO3 to moles KClO3. To make this easier, know the molecular mass of KClO3 is 122.55 g/mol.

Theoretical Yield Example Step 1

Theoretical Yield Example Step 2

Theoretical Yield Example Step 3

6 = x moles KClO3

Step 2: Use the chemical equation to relate moles KClO3 to moles O2.

From above, we see 2 moles of KClO3 will produce 3 moles of O2 gas.

Theoretical Yield Example Problem Step 4

Theoretical Yield Example Problem Step 5

Theoretical Yield Example Problem Step 6

x moles O2 = 3 x 3 moles O2
x moles O2 = 9 moles O2

6 moles of KClO3 (735.3 grams of KClO3) will produce 9 moles of O2 gas.

Cosmic Background Periodic Table – Free Printable

The colorful printable periodic table features a cosmic or space-themed background. You can use the 1920 x 1280 pixel cosmic background periodic table as a wallpaper for your desktop or mobile device, too.

Cosmic Background Periodic Table

Cosmic Background Periodic Table

We chose not to color the element groups for this table. This periodic table features element names, symbols, atomic numbers, and atomic weights. The table is new for 2016, using the most recent atomic data.

We’ll be adding a PDF of this table. Post a comment if there are other options you’d like to see!

Get the Cosmic Background Periodic Table

Periodic Table Poster

Periodic Table Poster

Download the periodic table by right-clicking on the image and saving it to your device. For best printing results, choose landscape orientation and “fit to print” to completely fill the page.

If you need a larger periodic table, this image is available as a poster on Redbubble in a variety of sizes, up to 47″ x 31″.




What Are Some Examples of Chemistry in Daily Life?

Examples of chemistry in daily life include cooking food, digesting it, using soap to clean your skin, and burning gas to run your car. (Raymond Bryson)

Examples of chemistry in daily life include cooking food, digesting it, using soap to clean your skin, and burning gas to run your car. (Raymond Bryson)

You encounter chemistry every day, yet might have trouble recognizing it, especially if you are asked as part of an assignment! What are some examples of chemistry in daily life? Share your examples or read reader submissions.’

Examples of Chemistry in the Real World

There are many examples of chemistry in daily life, showing how prevalent and important it is.

  • Digestion relies on chemical reactions between food and acids and enzymes to break down molecules into nutrients the body can absorb and use.
  • Soaps and detergents act as emulsifiers to surround dirt and grime so it can be washed away from clothing, dishes, and our bodies.
  • Drugs work because of chemistry. The chemical compounds may fit into the binding site for natural chemicals in our body (e.g., block pain receptors) or may attack chemicals found in pathogens, but not human cells (e.g., antibiotics).
  • Cooking is a chemical change that alters food to make it more palatable, kill dangerous microorganisms, and make it more digestible. The heat of cooking may denature proteins, promote chemical reactions between ingredients, carmelize sugars, etc.

medicinal effect

Medicines are the best example of chemistry which save us from diseases and make us able to live. They contain the chemical compound.
—aim

All is chemistry

Everything is the product of chemistry. In morning we use toothpaste which is chemistry product. And at night when we go to bed we burn a coil which also works as chemical to keep mosquito far from us.
—Animesh

CENTRAL SCIENCE

medicine, engineering, agriculture and all other fields are dependent on chemistry. so yes, it is important to know it
—future nurse

Drug – Food Interactions

You can apply chemistry in your daily life to make sure any drugs you use aren’t compromised or overly strengthened by the foods you eat. For example, many drugs are affected by alcohol. Some medications are negated by eating something as seemingly harmless as grapefruit! Others contain caffeine as an active ingredient, so if you take the medicine with coffee or cola, you’re increasing your dosage.
—gemdragon

CHEMISTRY is a powerful subject

“chemistry makes many thing” I say, not a chemistry in world but condition of the world? I can’t dream it !!!!! chemistry is a mind blowing creativity & imagination subject chemistry is a god’s gift.
—aravind scorpio

chemistry in clothing

colours to the cloths which are we are wear is due to azo dye (organic compound)
—RG veena

Chemistry

Chemistry is useful in our daily lives.. So, guys without chemistry….? Oh.. Don’t think that.. Chemistry will always with us..
—Kalai

Chem. in B.Tech

all u know B.tech (except Chemical Engg.) looks sound without chemistry.But it is a fact that for all type substances used in branches like ELE,ENTC,CV,MECH,CSE or IT can”t be imagined without the knowledge of CHEM.e.g.Chips in COMPUTERS is made up of Carbon &Silicon. Electricity is due to the gift Chem. in form of ELECTRON.
—P Katual

Salt-Nacl

Our food is not tasty without salt. Salt is the essential one for us. That salt is also a chemical compound only. Sodium Chloride has an international standard that is created by ASTM International. The standard is named ASTM E534-13 and it is the standard test methods for chemical analysis of sodium chloride. These methods listed provide procedures for analyzing sodium chloride to determine if it is suitable for its intended use and application.
—Tarun Omer

chemistry is life

Think living without WATER or AIR or SUN or YOUR FAV SNACK! YES we are NOTHING without CHEMISTRY!!!
—swati

chemistry

chemistry is the branch of science which deals with matter and its properties or compositions ….
—aarti

chemistry for washing

Chemicals make our clothes clean. Not only clothes but we also use chemicals to wash utensils.
—swetha

tree attraction

we see every day on road sides different kinds tree exist. And their upper parts(leafs and thin woods) are attracted to each other from both sides of road , which is actually hydrogen bonding . We know water has hydrogen bonding so trees and their leafs have water. That is why their upper parts are attracted. Good luck
—junaid bangash

Cosmetics

how the best chemicals can make you look attractive
—shikhar

chemistry in construction

The cement and other materials that we use in construction of houses eg paints,plaster of paris and many other are tha products of chemistry
—Hamna Riaz

CHEMISTRY

CHEMISTRY IS ONE OF THE INTERESTING SUBJECT. I LIKE THIS SUBJECT VERY MUCH . AS YOU KNOW THAT CEMISTRY IS ONE OF THE Dangerous subject
—ANIKET LANJEWAR

Chemistry in cooking.

It is very interesting to know that chemistry is used in cooking manner.For example in our lunch ,our main food is rice which is obtained by the indirect use of chemicals.Like wise, spoon by which we make curry is also made up of chemicals.Various vegitables are also obtained by the large use of chemicals.Oils are also the combinations of chemicals.So in totality in our fooding chemistry has a vital role.
—Satya ranjan jena.

examples of chemistry

fertilizers r 1 of d bst exmple of chemistry….. Now a days injections arr injected in fruits or vegetables so they could sell… Now the time will soon come that human can inject their children so that they could not face any problem in nourishing their children……. Then it will soon become passion for all
—savita

Chemistry Word Search Puzzle

Add a little fun to learning chemistry vocabulary. This chemistry word search contains vocabulary words associated with the science of chemistry. The terms can be found horizontally, vertically and diagonally. Click the image below to view the full sized version or download a PDF version for printing.

Chemistry Word SearchFor the people that need a little extra help, take a peek at the solution to the puzzle. A PDF version of the solution is also available.

Concentration Units For Solutions

Beaker and FlaskChemistry is a science which deals a lot with solutions and mixtures. Knowing just how much of one thing is mixed in with a solution is an important thing to know. Chemists measure this by determining the concentration of the solution or mixture.

There are three terms that need to be defined in concentration discussions: solute, solvent and solution.

Solute: The dissolved substance added to the solution.
Solvent: The liquid that dissolves the solute.
Solution: The combination of solute and solvent.

The relationship between these three terms is expressed by many different concentration units. The unit you choose to use depends on how the solution is going to be used in your experiments. Common units include molarity, molality, and normality. Others are mass percent, mole fraction, formality and volume percent. Each unit is explained along with information about when to use them and the formulas needed to calculate the unit.

Molarity

Molarity is the most common concentration unit. It is a measure of the number of moles of solute in one liter of solution. Molarity measurements are denoted by the capital letter M with units of moles/Liter.

The formula for molarity (M) is

This shows the number of moles of solute dissolved in a liquid to make one liter of solution. Note the amount of solvent is unknown, just that you end up with a known volume of solution.

A 1 M solution will have one mole of solute per liter of solution.  100 mL will have 0.1 moles, 2L will have 2 moles, etc.

Molarity Example Problem

Molality

Molality is another commonly used concentration unit. Unlike molarity, molality is interested in the solvent used to make the solution.

Molality is a measure of the number of moles of solute dissolved per kilogram of solvent. This unit is denoted by the lower case letter m.

The formula for molality (m) is

molality formula

Molality is used when temperature is part of the reaction. The volume of a solution can change when temperature changes. These changes can be ignored if the concentration is based on mass of the solvent.

Molality Example Problem

Normality

Normality is a concentration unit seen more often in acid-base and electrochemistry solutions. It is denoted by the capital letter L with units of moles/L. Normality is more concerned with the chemically active part of the solution. For example, take two acid solutions, hydrochloric (HCl) acid and sulfuric (H2SO4) acid. A 1 M solution of HCl contains one mole of H+ ions and one mole of Cl ions where a 1 M solution of H2SO4 contains 2 moles of H+ ions and one mole of SO4 ions. The sulfuric acid produces twice the number of active H+ ions as the same concentration of HCl. Normality addresses this with the idea of chemical equivalent units. Equivalent units are the ratio of the number of moles of solute to the number of moles needed to produce 1 mole of the active ion. In our example, this ratio is 1:1 for HCl, both H+ and Cl ions so the equivalent unit for both ions is 1. For H2SO4, the ratio is 1:12 for H+ and 1:1 for SO4. The equivalent unit for H+ is 2 and 1 for SO4.

This number is used to calculate the normality of a solution using the formula

Note it is essentially the same as the molarity equation with the addition of equivalent units.
For our example, the 1 M solution of HCl would have a normality of 1 N for both H+ and Cl and the 1 M H2SO4 would have a normality of 2 N for H+ and 1 N for SO4.

Mass Percent, Parts per Million and Parts per Billion

Mass percent or mass percent composition is a measurement to show the percentage composition by mass of one part of a solution or mixture. It is most often represented by a % symbol.

The formula for mass percent is

where A is the part needed and the total is the total mass of the solution or mixture. If all the mass percent parts are added together, you should get 100%.

Mass Percent Example

If you think of mass percent as parts per hundred, you can make the leap to the units of parts per million (ppm) and parts per billion (ppb). These two units are used when the solute’s concentration is very small compared to the volume measured.

The formula for parts per million is

and parts per billion

Note the similarity between mass% and these two equations.

Volume Percent

Volume percent is a concentration unit used when mixing two liquids. When pouring two different liquids together, the new combined volume may not be equal to the sum of their initial volumes. Volume percent is used to show the ratio of the solute liquid to the total volume.

The formula is very similar to the mass percent, but uses volume in place of the mass. VolumeA is the volume of the solute liquid and the volumeTOTAL is the total volume of the mixture.

On a side note, v/v % measurements of alcohol and water are labelled commercially with the unit known as Proof. Proof is twice the v/v % measurement of ethanol in the beverage.

Mole Fraction

Mole fraction is the ratio of the number of moles of a single component of a solution to the total number of moles present in the solution.

Mole fractions are often used when discussing mixtures of gases or solids, but could be used in liquids. Mole fraction is denoted by the Greek letter chi, χ. The formula to calculate mole fraction is

Formality

Formality is a less common concentration unit. It appears to have the same definition as molarity with the formula:

Notice how the only difference between formality and molarity is the letters F and M. The difference is formality disregards what happens to the solute after it is added to the solution. For example, if you take 1 mole of NaCl and add it to 1 liter of water, most people would say you have a 1 M solution of NaCl. What you actually have is a 1 M solution of Na+ and Cl ions. Formality is used when it matters what happens to the solute in the solution. The above solution is a 1 F solution of NaCl.

In solutions where the solute does not dissociate, such as sugar in water, the molarity and formality are the same.

October 2014 In Chemistry

October is a busy month for chemists. This year, October in Chemistry has the Nobel Prize, National Chemistry Week and Mole Day!

Nobel Prize

Nobel Prize medallion awarded to Nobel Prize recipients.

Nobel Prize – October 6

The Nobel Prizes are typically announced at the beginning of the month of October. This year, the Prizes will be announced October 6 through October 10. Physiology and Medicine on Monday, Physics on Tuesday, Chemistry on Wednesday, Peace on Thursday and Economics on Friday. Literature will be announced at a later date.

The scheduled announcement for the Chemistry Prize is “11:45 am CET at the earliest”. You can watch the announcement online on the nobelprize.org’s YouTube channel.

National Chemistry Week 2014National Chemistry Week – October 19-25

Every year, the American Chemical Society arranges National Chemistry Week to raise awareness of the important role of chemistry in our lives. This year, National Chemistry Week is October 19-25 and the theme is “The Sweet Side of Chemistry: Candy”.

The ACS’s National Chemistry Week website contains links to community events, educational resources and other useful information about National Chemistry Week. One of my favorites is the kid’s hands on activity book (PDF file). You don’t have to be a chemist to enjoy sweet chemistry. Check it out for yourself.

Mole Day Mascot

Mole Day Mascot Credit: National Mole Day Foundation www.moleday.org

Mole Day – October 23

Mole Day is an unofficial holiday. Chemists like to recognize what many consider ‘their unit’ of measurement—the mole. One mole of something is equal to Avogadro’s number of something, or 6.022×1023 somethings. Mole day is celebrated on 10-23 each year from 6:02 am to 6:02 pm.

Although the celebration is unofficial, there is a National Mole Day Foundation that attempts to get all people enthusiastic about chemistry. They have assigned themes to Mole Day celebrations since 1991. This year’s theme is Mole-O’Ween. This should prove a nice addition to the National Chemistry Week celebration involving candy chemistry.

Today In Science History – July 13

August Kekulé

Friedrich August Kekulé von Stradonitz. (1829-1896) German chemist

July 13 marks the passing of one of the most prominent chemists of the 19th Century, August Kekulé.

Kekulé is credited as the man who discovered the tetravalence of carbon, carbon atoms could bond to other carbon atoms and discovered the bonding order of atoms in a molecule. He was the first to draw chemical structures where atoms were connected by lines to represent the bonds between them.

Kekulé’s theory of molecular bonding would chain together atoms by their valence charges. This allowed chemists to better understand and visualize what the molecule looked like. This in turn allowed chemists to predict what it would take to break apart molecules and synthesize new ones. While this theory was more of a rule of thumb and many exceptions could be found, it’s use greatly advanced organic chemistry in a short amount of time.

Benzene 3D

3D Ball and Stick model of the benzene molecule. Credit: Todd Helmenstine

Kekulé is often credited for discovering the ring structure of the benzene molecule. Benzene consists of six carbon atoms forming a ring, with one hydrogen atom bonded to each carbon. Kekulé wrote about the method of his discovery where he was sitting by the fireplace and started to nod off. He dreamed of atoms arranging themselves in groups of ever increasing size until they became long chains. The chains started to wind and turn like snakes until one snake grabbed its own tail. He woke up suddenly and spent the rest of the night working out the structure. It just goes to show that if you let your mind wander, you may figure out a solution to a problem. That, or it shows chemists can have some strange dreams.