Steps for Finding the Empirical Formula You can find the empirical formula of a compound using percent composition data. If you know the total molar mass of the compound, the molecular formula usually can be determined as well. The easiest way to find the formula is:
Assume you have 100 g of the substance (makes the math easier because everything is a straight percent).
Consider the amounts you are given as being in units of grams.
Convert the grams to moles for each element.
Find the smallest whole number ratio of moles for each element.
Empirical Formula Problem Find the empirical formula for a compound consisting of 63% Mn and 37% O
Solution for Finding the Empirical Formula
Assuming 100 g of the compound, there would be 63 g Mn and 37 g O
Look up the number of grams per mole for each element using the Periodic Table. There are 54.94 grams in each mole of manganese and 16.00 grams in a mole of oxygen.
63 g Mn × (1 mol Mn)/(54.94 g Mn) = 1.1 mol Mn
37 g O × (1 mol O)/(16.00 g O) = 2.3 mol O Find the smallest whole number ratio by dividing the number of moles of each element by the number of moles for the element present in the smallest molar amount. In this case there is less Mn than O, so divide by the number of moles of Mn:
1.1 mol Mn/1.1 = 1 mol Mn
2.3 mol O/1.1 = 2.1 mol O
The best ratio is Mn:O of 1:2 and the formula is MnO2The empirical formula is MnO2
Opt for wholegrain food Walk into a room and forget why you're there? Forget already what this article's about? Make sure you're eating a diet rich in a mix of wholegrain foods such as cereals, wheatbran, wheatgerm and wholewheat pasta. One study found that women who increased their folic acid, vitamin B12 and vitamin B6 intake showed an improvement in recalling information compared to women who were not taking a supplement.
Enjoy oily fish
The essential omega-3 fatty acids - found in oily fish, as well as fish oil, walnut oil and flaxseeds (linseeds) - are high in DHA, fatty acid crucial to the health of our nervous system. Low DHA levels have been linked to a higher risk of developing Alzheimer's disease and memory loss. Fish also contains iodine, which is known to improve mental clarity. Binge on blueberries Research from Tufts University in the United States and published in the Journal of Neuroscience suggests that blueberry extract can improve short term memory loss. Widely available, so there's no excuse!
Eat more tomatoes
There is good evidence to suggest that lycopene, a powerful antioxidant found in tomatoes, could help protect against the kind of free radical damage to cells which occurs in the development of dementia, particularly Alzheimer's.
Math is a unique subject. It involves symbols, formulas, specific procedures, textbooks that look different, and many unique words and terms. Consequently, it is important to use study skills that apply particularly well to math. Here are some you should use.
You can't learn math just by reading and listening. Much of math learning involves actively doing. This means that you must do all of your math homework and assignments. This is essential to learning how to use formulas and procedures.
Math is a sequential subject. What is taught on a given day is based upon what was taught before. Once you fall behind, it is very difficult to catch up. Cramming at the last minute will not help you. Be certain to attend every class and keep up with your teacher.
Math is a difficult subject that becomes increasingly complex. You may have to spend more study time on this subject than on your other subjects.
Don't try to memorize your way through math. There are simply too many formulas and procedures. Try to master the key concepts. This will reduce the amount of information you will need to remember.
Once you learn a procedure for solving a problem, that same procedure can often be used to solve other problems. When presented with a new problem, try to apply your past learning to the new problem.
Learn the vocabulary of math. Often, a word used in math has a different meaning than that same word when used outside of math. For example, volume in math refers to the amount of space within a solid figure. Outside of math, volume can refer to a book or to loudness. Write new math words and terms and their math meanings in a special place in your notebook.
Successful students have good study habits. They apply these habits to all of their classes. Read about each study habit. Work to develop any study habit you do not have. Successful students:
Try not to do too much studying at one time.
If you try to do too much studying at one time, you will tire and your studying will not be very effective. Space the work you have to do over shorter periods of time. Taking short breaks will restore your mental energy.
Plan specific times for studying.
Study time is any time you are doing something related to schoolwork. It can be completing assigned reading, working on a paper or project, or studying for a test. Schedule specific times throughout the week for your study time.
Try to study at the same times each day.
Studying at the same times each day establishes a routine that becomes a regular part of your life, just like sleeping and eating. When a scheduled study time comes up during the day, you will be mentally prepared to begin studying.
Set specific goals for their study times.
Goals will help you stay focused and monitor your progress. Simply sitting down to study has little value. You must be very clear about what you want to accomplish during your study times.
Start studying when planned.
You may delay starting your studying because you don't like an assignment or think it is too hard. A delay in studying is called "procrastination." If you procrastinate for any reason, you will find it difficult to get everything done when you need to. You may rush to make up the time you wasted getting started, resulting in careless work and errors.
Work on the assignment they find most difficult first.
Your most difficult assignment will require the most effort. Start with your most difficult assignment since this is when you have the most mental energy.
Review their notes before beginning an assignment.
Reviewing your notes can help you make sure you are doing an assignment correctly. Also, your notes may include information that will help you complete an assignment.
Tell their friends not to call them during their study times.
Two study problems can occur if your friends call you during your study times. First, your work is interrupted. It is not that easy to get back to what you were doing. Second, your friends may talk about things that will distract you from what you need to do. Here's a simple idea - turn off your cell phone during your study times.
Call another student when they have difficulty with an assignment.
This is a case where "two heads may be better than one."
Review their schoolwork over the weekend.
Yes, weekends should be fun time. But there is also time to do some review. This will help you be ready to go on Monday morning when another school week begins.
These ten study habits can help you throughout your education. Make sure they are your study habits.
To do well on a test, you must have good knowledge of the information that is being tested. But you must also have a strategy for taking the test that allows you to show what you know. The DETER strategy can help you do your best on any test. Each letter in DETER reminds you what to do.
D = Directions
Read the test directions very carefully.
Ask your teacher to explain anything about the test directions you do not understand
Only by following the directions can you achieve a good score on the test.
If you do not follow the directions, you will not be able to demonstrate what you know.
E = Examine
Examine the entire test to see how much you have to do.
Only by knowing the entire task can you break it down into parts that become manageable for you.
T = Time
Once you have examined the entire test, decide how much time you will spend on each item.
If there are different points for items, plan to spend the most time on the items that count for the most points.
Planning your time is especially important for essay tests where you must avoid spending so much time on one item that you have little time left for other test items.
E = Easiest
The second E in DETER reminds you to answer the items you find easiest first.
If you get stuck on a difficult item that comes up early in the test, you may not get to answer items that test things you know.
R = Review
If you have planned your time correctly, you will have time to review your answers and make them as complete and accurate as possible.
Also make sure to review the test directions to be certain you have answered all items required.
Using the DETER strategy will help you do better on tests and get better grades.
It is important for you to be a good listener in class. Much of what you will have to learn will be presented verbally by your teachers. Just hearing what your teachers say is not the same as listening to what they say. Listening is a cognitive act that requires you to pay attention and think about and mentally process what you hear.
Here are some things you should do to be a good listener in class.
Be Cognitively Ready to Listen When You Come to Class. Make sure you complete all assigned work and readings. Review your notes from previous class sessions. Think about what you know about the topic that will be covered in class that day.
Be Emotionally Ready to Listen When You Come to Class. Your attitude is important. Make a conscious choice to find the topic useful and interesting. Be committed to learning all that you can.
Listen with a Purpose. Identify what you expect and hope to learn from the class session. Listen for these things as your teacher talks.
Listen with an Open Mind. Be receptive to what your teacher says. It is good to question what is said as long as you remain open to points of view other than your own.
Be Attentive. Focus on what your teacher is saying. Try not to daydream and let your mind wander to other things. It helps to sit in the front and center of the class, and to maintain eye contact with your teacher.
Be an Active Listener. You can think faster than your teacher can speak. Use this to your advantage by evaluating what is being said and trying to anticipate what will be said next. Take good written notes about what your teacher says. While you can think faster than your teacher can speak, you cannot write faster than your teacher can speak. Taking note requires you to make decisions about what to write, and you have to be an active listener to do this.
Meet the Challenge. Don't give up and stop listening when you find the information being presented difficult to understand. Listen even more carefully at these times and work hard to understand what is being said. Don't be reluctant to ask questions.
Triumph Over the Environment. The classroom may too noisy, too hot, too cold, too bright, or too dark. Don't give in to these inconveniences. Stay focused on the big picture
Temperature is the level of heat in a gas, liquid, or solid. Three scales are commonly used for measuring temperature. The Celsius and Fahrenheit scales are the most common. The Kelvin scale is primarily used in scientific experiments.
Celsius Scale
The Celsius scale was invented in 1742 by the Swedish astronomer, Anders Celsius. This scale divides the range of temperature between the freezing and boiling temperatures of water into 100 equal parts. You will sometimes find this scale identified as the centigrade scale. Temperatures on the Celsius scale are known as degree Celsius (ºC).
Fahrenheit Scale
The Fahrenheit scale was established by the German-Dutch physicist, Gabriel Daniel Fahrenheit, in 1724. While many countries now use the Celsius scale, the Fahrenheit scale is widely used in the United States. It divides the difference between the melting and boiling points of water into 180 equal intervals. Temperatures on the Fahrenheit scale are known as degree Fahrenheit (ºF).
Kelvin Scale
The Kelvin scale is named after William Thompson Kelvin, a British physicist who devised it in 1848. It extends the Celsius scale down to absolute zero, a hypothetical temperature characterized by a complete absence of heat energy. Temperatures on this scale are called Kelvins (K).
Converting Temperatures
It is sometimes necessary to convert temperature from one scale to another. Here is how to do this.
To convert from ºC to ºF use the formula: ºF = ºC x 1.8 + 32.
To convert from ºF to ºC use the formula: ºC = (ºF-32) ÷ 1.8.
To convert from K to ºC use the formula: ºC = K – 273.15
To convert from ºC to K use the formula: K = ºC + 273.15.
To convert from ºF to K use the formula: K = 5/9 (ºF – 32) + 273.15.
To convert from K to ºF use the formula: ºF = 1.8(K – 273.15) + 32.
