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Home-Work-2 (20 points)

For each of the following molecules or ions: draw the correct Lewis Dot Structure, give the molecular

geometry, electron geometry and draw the arrow indicating the direction of polarity. (Determine if the

molecule is polar or nonpolar)/Include all resonance structures.

MgCl2

Molecular Geometry: Linear

Electron Geometry: Linear

Polar: its ionic bond

CHCl3

a)b) Molecular geometery is tetrahedral

Cl

lH-C-Cl

l

Cl

c) Yes. Its polar

d) Electron Geometry: tetrahedral

OF2

Molecular Geometry: tetrahedral

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Electron Geometry: tetrahedral

Polar: yes. Its Polar

PCl3

a) molecular geometry: trigonal pyrimida

a) Electronic geometry : tetrahedral

b) PCl3 is polar

Pre-Lab Quiz-3

1. What is the value of Avagadros #?

This experimentally determined value is approximately 6.022 x 1023

particles per mole.

2. Define Avagadros number.

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Avogadro's number is the number of particles found in one mole of a substance. It is the

number ofatoms in exactly 12 grams ofcarbon-12.

3. Calculate the number os atoms in 3.5 grams of P2O5

Given: 3.5 gram

solution

mass of P2O5 =2*30.974+5*16=142 gram/mol

oxygen atom= 3.5 gram*(1 mole of P2O5/142gram/mol)*(5 mole oxygen/1 mole

P2O5)*(6.022*10^23 atoms /mole O)=7.4190140845070422535211267605634*1022

4. How would you caliberate your pipette?

Step1: check accuracy and precision at highest setting of volume

Step2: repeat same procedure for lowest volume setting

Step3: if necessary adjust pipet at lowest setting using calibration

Step4: Adjust and measure until pipet is accurate

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1. Clean the Pipette: Thoroughly clean the pipette as well as the beaker. Dry it out completely.

This is done to get rid of any past residue that may affect the results.22. AddDistilled Water: Put some distilled water in an Erlenmeyer flask. Let it stand out on a

bench for about 15 minutes. Now, measure the temperature of the water.33. Beaker Mass Measurement: Find out the mass of the beaker to the nearest tenth of a

milligram, using a balance.44. Taking Help of Pipette Filler: Now, using a pipette filler fill the pipette with the water from

the flask. Move this water into the beaker. Weigh the beaker again. Note down the differencein weight of the beaker and calculate the mass of water discharged. Carry out this processthree more times.

5. 5Calculate and determine: Calculate and determine the mean of the four pipettemeasurements.

6. Adjusting the Buoyancy of Air: Make an addition of 1.06 mg per gram to the mean mass toadjust for the buoyancy of air during the weighing. Do not follow this step in case you areusing a digital scale.

7. Calculating Density of Water: Calculate the density of water at the temperature youmeasured earlier in the process. Determine the mean volume of water discharged by thepipette using the formula: Volume = mass / density.

8. Compare Measurements & Calculations: To check the precision of your pipette make acomparison of your measurement and calculations to other results in pipette calibration.

Pre-Lab Quiz-2

1. What is the detergent doing to the water?

When detergent placed in water it produce exothermic reaction that producesheatas chemical

bond energy is converted into thermal energy.

http://www.wikihow.com/Do-Pipette-Calibrationhttp://www.wikihow.com/Do-Pipette-Calibrationhttp://www.wikihow.com/Do-Pipette-Calibrationhttp://chemistry.about.com/b/2013/05/01/exothermic-detergent-reaction.htmhttp://chemistry.about.com/b/2013/05/01/exothermic-detergent-reaction.htmhttp://chemistry.about.com/b/2013/05/01/exothermic-detergent-reaction.htmhttp://chemistry.about.com/b/2013/05/01/exothermic-detergent-reaction.htmhttp://www.wikihow.com/Do-Pipette-Calibration

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2. What would happen if you look directly at the burning Magnesium? ( 1pt)

The bright white light produced by burning magnesium contains ultraviolet light that can

permanently damage eyes.

3. Write the decomposition reaction for peroxide. ( 1pt)

Its a decomposition reaction

2H2O2+catalyst-----> 2H2O +O2

4. What are physical & chemical properties? Give two examples of each one of them. ( 2pts)

Physical properties: are the characteristics of matter that can be changed without changing its composition

These characteristics are directly observable or measurable

E.g. Size, Shape, Mass, Density, Conductivity

Chemical properties:are the characteristics of a substance that determine the tendency of the matter totransform in composition as a result of the interaction with other substances

These are characteristics that describe the behavior of matter

E.g. Flammability, Solubility, reaction

5. Where would you dispose off the peroxide waste? _______________________________ ( 1pt)

In secured waste disposal site