The corundum (Al2O3) has a rhombohedral Bravais lattice, but it closely approximates a hexagonal lattice and is usually regarded as hexagonal. There are 30 ions per lattice site (and per unit cell). The Al2O3 formula requires that these 30 ions be divided as 12Al3+ and 18 O2-. The Al2O3 structure closely approximates close-packed O2- sheets with two-thirds of the small interstices between sheets filled with Al3+. In other words, close-packed O2- ion containing layers have repeated stacking and the Al3+ ions fill two-thirds of the octahedral interstices between adjacent layers. (22 points) The density of Al2O3 is Al2O3 = 3.8 gram/cm3, Atomic masses are : MAl = 26.98 gram/mol, MO = 16.00 gram/mol Ionic radii are : rAl3+ = 0.05 nm, rO2- = 0.14 nm a) Draw 3 layers/sheets of O2- ions and Al3+ ions in between them. b) Draw the corundum unit cell and show the O2- and Al3+ ions in the unit cell. c) How many Al2O3 molecules are there in 1 cm3 ? How many atoms are there in 1 cm3 of Al2O3? d) How many Al2O3 molecules are there in 1 gram? How many atoms are there in 1 gram of Al2O3? e)Calculate the atomic packing factor of Al2O3

You have a 5.00 g sample of an unknown compound. After analysis you find that its percent composition is 54.5% carbon, 9.10% hydrogen and 36.4% oxygen.

What is the empirical formula for this compound?

If the molar mass of this compound is 132 g/mol, what is its molecular formula?

When you are waiting for the crystals to appear in a recrystallisation experiemnt you should not cool the flask from hot to ice cold because you will cause ......... to happen rather than crystallisation.

1. You have 0.95ft^3 aluminum(density=2700kg/m3,MW=26.98). Calculate the mass in kg, lbm, gmole and lbmole.

2. Assume there are 39 inches in a meter.What is the external surface area in the SI system of a sphere that is 9.0 inches in diameter? Determine the volume in cubic feet. (Note SI system: meters / kg / Newtons etc.)

3. If a US gallon has a volume of 0.134 ft3 and a human mouth has a volume of 0.950 in3, how many mouthfuls of water are required to fill a 7.5 US gallon can?

4. Convert the following:

a) 3.9cm/s to ft/min

b) 187 lbm ft/min2 to kg cm/s2

c) 55 ft3 to gallons

d) 920mg to ounces

e) 2lbm/ft.hr to g/cm.s

5. Water at 4C has a density of 1.0g/cm3 and a molecular weight of 18. What is the density in the following units:

a) kg/m3

b) lbm/ft3

c ) kmol/L

6. Do the following conversions:

a) 1.6 x 10^-2 g cm-1s-1 to lbm ft-1 s-1
b) What is the molecular weight of propionic acid (C2H5COOH).

c) How many kg are there in 10 lb mol of sodium hydroxide (NaOH)

Dissolve 1 mole of Succinic Acid into 1 Liter of water. What is the pH of the solution? What is the molarity of the protonated and depronated forms of Succinic Acid?

calculate the molar volume of hydrogen gas using the newton-raphson method 40 atm and 300 K

R=0.08206 dm³ atm K^-1

for Hydrogen Van der Waals constants a=0.244 dm⁶ atm mol^-2 ,b=0.0266 dm³ mol^-1    

consider the rotation of 50.0mL of a 0.2M HNO3 with 0.10M NaOH calculate the pH of the solution

a) before any extra NaOH has been add
b) after 50mL of NaOH
c) add 100mL of NaOH
d) add 150mL of NaOH

Is Atomic Mass and Atomic Weight the same terms? Or is Atomic mass and Mass Number the same terms?

On the MCAT Kaplan books it says that atomic mass and mass number are the same thing but online and other chemistry textbooks, atomic mass and atomic weight are the same thing.

Can someone please clarify which two terms are the same thing or are they all different? I really need help to make sure I understand this for the MCAT.

suppose that the reservoir contains 1.5L of 2.0M K2PO4. For how many hours can the reservoir provide 20mM KOH at a flow rate of 1.0 ml/min if 75% consumption of K+ in the reservoir is feasible

22. Draw the structure of two steroid hormones and name their use in humans.  

23. Draw 3 amino acid structures explain their primary uses and sources of the amino acids.

24. Explain the four components of the protein tertiary structure.

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Write the net equations, the standard cell potential, and the number of electrons transferred in the following electrochemical cells.

Instructions:

Enter all substances in the order listed at the top of the column.

Use a carot to indicate a superscript, but do nothing for subscripts.

Use a hyphen + greater than (->) for yields.

Click on the eye symbol to check your formatting.

Pt/I₂,I^1-//Au³⁺/Au

What is the difference between Addition and Condensation reactions? How does this relate to polymers?

Write a balanced nuclear equation for the following:
When iridium-192 emits a beta particle as it decays

Compare and contrast the molecular structure and performance characteristics of LDPE and HDPE. Provide an example of each type of polymer

Describe two types of methods that can be used to mold plastic products.

Tin (Sn), with a mass number of 126 and an atomic number of 50, decays by beta emission. Identify the product of the nuclear reaction by providing its atomic symbol (2 points), mass number (2 points), and atomic number (1 point).

Uranium (U) has a mass number of 238 and an atomic number of 92 and decays by emission of an alpha particle. The product of this decay is (Points : 5)        uranium (U), with a mass number of 234 and an atomic number of 92.
       lead (Pb), with a mass number of 234 and an atomic number of 91.
       thorium (Th), with a mass number of 234 and an atomic number of 90.
       radium (Ra), with a mass number of 234 and an atomic number of 88.
       thorium (Th), with a mass number of 234 and an atomic number of 91.

Without drawing out correlation diagrams in detail for each 2^nd period homonuclear diatomic molecule separately please show how simple MO theory explains the trends observed in the properties of these molecules shown in the graph. Recall that there are two different energy level orderings, one for Li₂ through N₂ and a different one for O₂ and F₂. You might wish to draw these out separately and write out the electron configurations to explain your answer. Please include the ions in your response.