More Unit Conversions

Today we learned about conversions.

We started today looking at some more problems and explanations of molar mass and how to use it. Again molar mass is just the mass of 1 mole in grams. This is found on the periodic table and it is the atomic mass.

Look on the last post for examples of what the equations look like.

One of the most important things we learned today was that EVERYTHING must go through moles.

If it is Grams to Particles,it has to go through moles and if it is Particles to grams then it also has to got through moles.

We then did some learning checks problems like the Nutra-sweet problem. For problems like those to calculate the molar mass of something you take each element and treat it like its own part. For the Nutra- Sweet problem it would look like this

C14H18N2O5

(12x14) + (1x18) +(14x2)+(5x16). this is how you find the molar mass of a compound, then you complete the problem like a simple one.

After that we then had the rest of the class period to work with our partners on the Mole Workshop. Those problems are tricky they just need to be thought out and make sure to show your work. Remember that only one person in your pair needs to turn it in tomorrow but it is best if both partners do the work. I am sorry that I can not post the notes on here, I can not seem to find them on slideshare but if you have any questions just post it here or ask a teacher. This website http://www.chem1.com/acad/webtext/intro/MOL.html could also assist you.

Homework tonight: Finish the Mole Workshop and the other Mole worksheet

Study for the quiz tomorrow over dimensional analysis and unit conversions.

Test is coming up the 28th.

Alright well thats all I have have fun studying.

next scribe is Trevor. have fun

Bobby

I want a Number and Guacamole Named after Me

Hey sorry for the late post but this is for yesterdays.

To start of the day we went over the test we took on Friday and were told if we needed any help naming, the best thing to do was practice and more practice. After that we started looking at our notes about Avogadro's number. That number would be the mole. Is written in scientific notation as 6.02x10^23 or 602 billion trillion or 602,000,000,000,000,000,000,000. My recommendation is to keep it in scientific notation. The mole is only used when talking about Particles and molecules, things that are REALLY small. The mole is used in the same way that a dozen is used.

Ø 1 dozen cookies=12 cookies

Ø 1 mole of cookies=6.02x10^23

Ø 1 dozen cars=12 cars

Ø 1 mole of cars=6.02x10^23

The number will always be the same but the mass will be different. on a side note- mole is abbreviated as "mol" but in liebs class we feel that we deserve our own symbol that is shorter and more convenient so we chose a circle with a line through it. I would post the notes here but I can’t find them, they are not on slide share so I will just go on to conversions.

6.02x10^23/ 1 mol OR 1 mol/ 6.02x10^23 will always be used it depends on what you are trying to get. I will discuss which one to use in the section about general concepts below.
After we talked about Avogadro's number we went on to molar mass.

Molar mass is the mass of 1 mole in grams. This number is equal to the numerical value of the atomic mass found on the periodic table. For example:

Ø 1 mole of H atoms = 1.008g

Ø 1 mole of C atoms = 12.0g

Ø 1 mole of Bi atoms = 209.0g

As i am finishing up i will end with some general concepts to keep in mind when dealing with calculations involving moles

Ø For moles to particles, multiply by Avagadro's number (mole)

Ø For particles to moles, divide by Avagadro's number (mole)

Ø For grams to moles, divide by molar mass

Ø For moles to grams, multiply by molar mass

Well I am done for now - if you want to get a sense of how big a mole actually is you can check this out, http://www.youtube.com/watch?v=1R7NiIum2TI . This video is just showing how insanely big a mole is. Have fun

The next scribe is me. so until later tonight, have fun working on the worksheets we got and studying for the quiz tomorrow over conversions using moles and such and dimensional analysis.

Unit Conversions

In chemistry today we started our first day of chapter three. In this section we learned about unit conversions. D Liebs gave us notes and lectured us for the majority of the class. You can find the notes on Moodle. Anyway first we discussed unit factors. A unit factor is basically a ratio. For example, if you want to say, there are 5280 feet in 1 mile, you would write it as: 5280 ft/1 mile. This is an example of a unit factor.

Here is an example of a unit conversion problem:

Convert 45 miles per hour to feet per second. Well to solve this problem first set up this fraction:

45 mi/1 hr

Now we have to multiply this unit factor by many others so that we can get the units to be feet per second. To do this, first think how many seconds are in one hour. Well there are 3600 seconds in one hour, so set up the fractions next to each other like this:

45 mi/1 hr * 1 hr/3600 sec

Note that in the first unit factor the hours is in the denominator. But in the second unit factor the hours is in the numerator. You must set up the units like this so that when you multiply across, the units will cancel out.

Now you have to cancel out the miles. But we need to think about how many feet are in one mile because we are trying to get feet/second. So now we multiply the fractions like this:

45 mi/1 hr * 1 hr/3600 sec * 5280 ft/1 mi

Remember to put the miles in the denominator, because in the first fraction the miles are in the numerator. Okay the last step is to multiply all of the numerators together and then divide that number by all of the denominators. So you do:

45 x 1 x 5280=237600
237600 / 3600= 66

Now you cancel out the units and you are left with feet in the numerator and seconds in the denominator. So the answer is 66 ft/1 sec.
After D Liebs explained the notes and such he gave us the rest of the class period to work on the worksheets with solving unit conversions. I know I was supposed to post this a little while ago but Blogger was not working. I also wanted to put some real fractions in the blog but copy and paste does not work well in Blogger. Well that's all for today, the homework was the WebAssign and complete the unit conversions worksheets.

Next scribe is................................................ Robert S.