Tutorial for Ray Only

lab6 xitem_number_3_formula_mass_computations xitem_number_5_formula_mass_computations x

Hi Ray,

 

Please see  attached file. They are the solutions to Lab6 . If you have extra time, please review them. After that, you may already submit them yourself or you can send it back to me if you found something  that needs to be modified. 

 

Lab 6 document  are the questions of the lab and answersand the other two are the ‘show work’ requirement as required in the lab.

 

Thanks..

 

Roel

Refer to a periodic table, as needed, to answer these questions.

Section 1: In-Class Practice

1. How does the structure of an ionic compound differ from that of a molecular compound?

Ionic

compounds are formed by the transfer of electrons while molecular compounds are formed by sharing of electrons. In addition to that, ionic compounds are formed via ionic bond between a metal and non-metal while molecular compounds are formed via covalent bond between two non-metals.

2. Distinguish among the terms molecular mass, formula mass, and molar mass (the mass of a mole).

Molar mass is the mass of one mole of a substance. For example the molar mass of

H2O

is 18.015 grams.

Formula and molecular mass are measured in terms of AMU (Atomic Mass Unit). Formula mass refers to the mass of an ionic compound. For example we refer to the 58.5 AMU mass of NaCl as its formula mass since NaCl is ionic. On the other hand, molecular mass refers to the 67.82 AMU mass of Boron Triflouride as molecular mass since it is a molecule.

3. Complete

Table 1

by

· Indicating whether each compound is ionic or molecular (Column 2)

· Noting whether each compound’s basic unit is a formula unit or a molecule (Column 3)

· Using the periodic table and a calculator to calculate the formula masses for each compound (Column 4)—show your work on a separate piece of paper

4. Calculate the formula mass of the hydrate, CuSO4 • 5H2O. Show your work.

Formula Masses (in amu):

Cu = 63.546 S = 32.065 O = 15.999 H = 1.008 O = 15.999

Mr = 63.546 + 32.065 + 4 (15.999) + 5 [2(1.008) + 15.999]

Mr = 249.7 amu

Section 2: Out-of-Class Practice

5. Complete

Table 2

by calculating the formula mass of each compound listed. Show your work on a separate sheet of paper.

6. Put a check beside each of the compounds in Table 2 for which you calculated the molecular mass.

7. Oxygen gas is diatomic, meaning that it is made up of two oxygen atoms. What would be the molecular mass of oxygen gas? Would it differ from the atomic mass of oxygen? If so, how?

Diatomic oxygen is O2.

Molecular

mass of oxygen gas = 2(15.999) = 31.998 amu

Thus, the molecular mass of oxygen gas is 31.998 amu. It differs from the atomic mass of oxygen gas since this value is only 15.999 amu.

8. What is the formula unit of aluminum chloride, Al2Cl6? What about the formula unit for ethane, C2H6? (Hint: Remember the difference between ionic and molecular compounds.)

The formula unit is the lowest ratio of ions represented in a compound. Thus, Al2Cl6 has a formula unit of AlCl3 with ions Al+3 and Cl-1. For C2H6, the lowest ratio is CH3.

 

Ionic

Formula Unit

Molecular

Molecule

Ionic

Formula Unit

Table 1
	Compound	Ionic/Molecular	Formula Unit / Molecule		Formula Mass (amu)
KCl			Ionic			Formula Unit	74.551
H2O		Molecular		Molecule	18.02
CaSO4	136.14
NH3	17.03
Hg(NO3)2	324.60

Compound

Formula Mass (amu)

Table 2
MgO	40.304
K2S	110.26
· C3H8O3	92.09
Ca(NO3)2	164.09
Mg3(PO4)2	262.84
· C6H2CH3(NO2)3	227.1
· Pt(NH3)2Cl2	300.1
Fe(ClO4)2	254.74
Na2CO3 • 10H2O	286.1
MgSO4 • 7H2O	246.5

Conclusion

Now address the Focus Question: Which has more mass—salt (NaCl) or sugar (C12H22O11)? Show calculations to support your answer.

Sugar (C12H22O11 has more mass than salt (NaCl) .

For NaCl:

Na = 22.99 Cl = 35.453

Mr = 22.99+ 35.453

Mr = 58.443 amu

For C12H22O11:

C = 12.011 H = 1.008 O = 15.999

Mr = 12(12.011) + 22(1.008) +11(15.999)

Mr = 342.3 amu

 

Item number 3 Formula Mass Computations (in amu) – Table 1

KCl

K = 39.098 Cl = 35.453

Mr = 39.098 + 35.453 = 74.551 amu

H2O

H = 1.008 O = 15.999

Mr = 2(1.008) + 15.999 = 18.02 amu

CaSO4

Ca = 40.078 S = 32.065 O = 15.999

Mr = 40.078 + 32.065 + 4(15.999) = 136.14 amu

NH3

N = 14.007 H = 1.008

Mr = 14.007 + 3(1.008) = 17.03 amu

Hg (NO3) 2

Hg = 200.59 N = 14.007 O = 15.999

Mr = 200.59 + 2[14.007 + 3(15.999)] = 324.60 amu

Item number 5 Formula Mass Computations (in amu) – Table 2

MgO

Mg = 24.305 O = 15.999

Mr = 24.305 + 15.999 = 40.304

K2S

K = 39.098 S = 32.065

Mr = 2(39.098) + 32.065 = 110.26 amu

C3H8O3

C = 12.011 H = 1.008 O = 15.999

Mr = 3(12.011) + 8(1.008) + 3(15.999) = 92.09 amu

Ca (NO3)2

Ca = 40.078 N = 14.007 O = 15.999

Mr = 40.078 + 2[14.007 +3(15.999)] = 164.09 amu

Mg3 (PO4)2

Mg = 24.305 P = 30.964 O = 15.999

Mr = 3(24.305) + 2 [30.964 + 4(15.999)] = 262.84 amu

C6H2CH3 (NO2)3

C = 12.011 H = 1.008 O = 15.999 N = 14.007

Mr = 7(12.011) +5(1.008) + 3[14.007 +2(15.999)] = 227.1 amu

Pt (NH3)2Cl2

Pt = 195.084 N = 14.007 H = 1.008 Cl = 35.453

Mr = 195.084 + 2[14.007+ 3(1.008)] = 300.1 amu

Fe (ClO4)2

Fe = 55.845 Cl = 35.453 O = 15.999

Mr = 55.845 + 2 [35.453 + 4(15.999)] = 254.74 amu

Na2CO3 • 10H2O

Na= 22.99 C = 12.011 O = 15.999 H = 1.008

Mr = 2(22.99) + 12.011 + 3(15.999) + 10[2*1.008 + 15.999] = 286.1 amu

MgSO4 • 7H2O

Mg = 24.305 S = 32.065 O = 15.999 H = 1.008

Mr = 24.305 + 32.065 + 4(15.999) + 7 [2*1.008 + 15.999] = 246.5 amu