Mole Conversions

There are two main types of mole conversions:

1. Gram to Mole Conversion
2. Mole to Gram Conversion
3. Particles to moles Conversion
4. Moles to Particles Conversion

First of all,
Let's see some Grams to Moles Conversion

Moles to Grams Conversions:



Conversions between particles and moles:

More information about Mole Conversions:



Chapter 4 Moles

Chapter 4 Moles



Avogradro and his mole number!

 

                                    What is a mole?

         A mole is a number, just like a dozen is the number 12.  However the mole number is called the Advagadro's number which is about 6.022*10^23.

Why do is mole so important in Chemistry?
-Acording to Avogadro's Hypotheses, Gas with equal volume at same temperature and pressure will have the same number of particles.


Equal volumes of gas, at the same temperature and pressure, contain the same number of molecules.-This means each of these gas will contain 1 mole and 1 mole more=6.022*10^23  partciles,unites or molecules



Review: Chapter 3

Significant Figures:
-measured or meaningful digits.
-can be precisedif there are many of them.
e.g 24.37  24.6

Accuracy:
-It is how close the measurement (or average measurement) comes to the accepted or real value.

Precision:
-It is how reproducible a measurement is compare to other similar measurements.

Absolute Uncertainty:
-the uncertainty expressed in the units of measurement, not as a ratio.

Relative Uncertainty:


-Relative Uncertainty =         Absolute Uncertainty
                                       ———————————
                                        Estimated Measurement


Density:
-defined as its mass per unit volume.

-formula of density:             Mass
                         D    =     ————
                                       Volume

Lab 2E Quiz and Graphing

Today we have just done a quiz on Lab 2E.

The quiz was just all about calculating the thickness of a certain object, such as alunminum foil.

Equation:

Density=Mass/Volume

If you want to calculation the thickness based on the information of an object:
Density=2.70g/cm^3
Mass=5.0g
The object Area=15cm by 16cm
And calculation the thickness:
It goes,
Volume=(2.70g/cm^3)/5.0g=0.54m^3
Thickness=0.54cm^3/15cm/16cm=2.25*10^-3cm

Next, we went to lab room and learnt how to graph base on the information of mass and volume.

 

Lab 2 E

               Today in class, we had an exciting lab on determining the thickness(height) of the aluminum foil.The lab was to help us get more familiar with sig figs, accuracy, precision, uncertainties and the formula of density.  Thus we all enjoy this super amazing lab!!!

Purpose: Find accurate and precise measurement of the thickness of the aluminnum foil expressed using correct number of sig figs.

Procedure

1. We start off by measureing all measuring the length and width of foil that is at least 15 cm on each side

2. Than we use the centigram to measure the mass of each foil.

3. After we calculated the Mass we than use the density formula to calculate the volume of the foil.

4. When we finished calculating the volume of the aluminum foil, we than use the lengh and width to calculate

the height because LxWxH=V

eg.V=0.36cm^3

L=15.60cm

W=15.35cm

Hight=0.36cm^3

--------------

15.60cm*15.35cm

=1.5*10^-3(Remember  round you sig figs till the very end!!)

5.  The final step is for us to calculate the experimental error when it comes to the accepted value for thickness of the aluminum foil which Mr.Chen gave us was 1.55*10^-3.

Formula Expremental error:

Experimental error=Your measurement-Accepted value

---------------------------------------------

accepted value *100

6.At the end of the experiment we wrote a conclusion on how accurate and precise

our messurement was.  Our measurement was precise because our experimental error

was only 3.2%. It was also precise because we got almost the same value each

time when we calcute the thickness of the foil for 3 trials.

Need more help go to:   http://www.mefeedia.com/watch/29045208

Note:Quiz next class on everything we done today on the lab !!!!

Density

Density:
-defined as its mass per unit volume.
-or, its weight per unit volume.
-Osmium is the most densest known substance at standard conditions for temperature and pressure.
-less dense fluids float on more dense fluids if THE FLUIDS DO NOT MIX.

 Here is an example of density between fluids.















-formula of density:             Mass
                         D    =     ————
                                       Volume


Example: An iron bar has a mass of 12.00 g and a volume of 1.25 L.  What is the iron bars density?

    As we know D=M/G, we could simply plug in the number, D=12.00g/1.25L which equals to 960 but don't forget the units! Its 960 g/L.

Leif Tung

Accuracy and Precision

Today, we have learnt the accuracy and precision of practises of measuring.
The following is the textbook definition:
Precision
It is how reproducible a measurement is compare to other similar measurements.

Accuracy
It is how close the measurement (or average measurement) comes to the accepted or real value.

Measurement and Uncertainty

- There are no measurment that is excact because every measurement is a best estimation with margins of error.

- Despite of have the best estimation, for example, there are 39 cars in a parking lot is an exact number because it's a set of objects.

Absolute Uncertainty

A measurement of the uncertainty which is expressed in units. There are 2 methods to find it:

Method 1: Make at least 3 measurements and calculate the average. In the other hand, the absolute uncertanty is the largest difference between the average and the lowest or highest reasonable measurement.

               - For example: when calculating the avery of a few data eliminate the unreasonable data first:

1. 59                          The average is 59
2. 60                          I have eliminated 53 because it is a absolute uncertainty.
3. 58
4. 53
5. 59

 Method 2: Determine the uncertainty of each instrument

• When you are making a measurement, make sure you measure the best estimation you can (precision). In some real practices, you should estimate whatever the smallest segment that is possible on a instrument scale.
• For exmple, our rulers have the smallest scale as 1 mm, so that the best precision should break down to 0.1 mm. When you are measuring a thing, you need to see more carefully and precisely to be certain of the 0.1 mm differences.

Relative Uncertainty and Significant Figures

Relative          Absolute uncertainty

uncertainty =--------------------------------------

                        Estimated measurement

That's about what we have learnt today.

Kevin Wang