Αt 20°C, elemental iron is bcc, a = 2.866 Å. At 950 °C, Fe is ccp, a = 3.43 Å. At each temperature, calculate: a) The density of iron, b) The metallic radius of iron atoms. For Fe: A = 55.85 g/mol

Suppose that 34.25 g of ice at -14.5

A sample of K(s) of mass 2.720 g undergoes combustion in a constant volume calorimeter at 298.15 K. The calorimeter constant is 1849 JK−1, and the measured temperature rise in the inner water bath containing 1439 g of water is 1.60 K.

a) Calculate ΔU∘f for K2O.

b) Calculate ΔH∘f for K2O.

the answer for ΔU∘f = -362 kJ⋅mol−1

and for ΔH∘f = -363 kJ⋅mol−1

how they got that answers ????

It has been quite difficult if not impossible to produce nanoparticles from organic materials (especially for medicine) like Ibuprofen, aspirin, etc. since they aggregate at normal conditions. Propose a possible method of producing nano ibuprofen and nanoaspirin and explain why that is more feasible than other methods. Please be as much quantitative in your proposal as possible.

A 3.900 g sample of a mixture of sodium hydrogen carbonate and potassium chloride is dissolved in 25.80 mL of 0.439 M H2SO4. Some acid remains after treatment of the sample. Write both the net ionic and the molecular equations for the complete reaction of sodium hydrogen carbonate with sulfuric acid. If 34.8 mL of 0.109 M NaOH were required to titrate the excess sulfuric acid, how many moles of sodium hydrogen carbonate were present in the original sample? What is the percent composition of the original sample?

Consider the triprotic acid, H3A; pKa1: 2.91; pKa2: 8.2; pKa3: 13.3. Calculate the pH and the concentrations of H3A, H2A-, HA2-, A3-, OH- and H3O+ at equilibrium in a 0.10 M solution of the triprotic acid.

Using data found in Appendix E of your textbook calculate the nonstandard emf for each of the following reactions if the concentration of each of the ions in these reactions is 0.0008 molar and everything else is standard (use 298 K for the temperature, R = 8.314 J/mol-K, and F = 96,485 C/mol):

(a) 1 Cl₂(g) + 2 Cr²⁺(aq) --> 2 Cl^-(aq) + 2 Cr³⁺(aq)   E = _____ V

(b) 1 Fe³⁺(aq) + 1 Na(s) --> 1 Fe²⁺(aq) + 1 Na⁺(aq)   E = _____ V

(c) 2 Li⁺(aq) + 2 I^-(aq) --> 2 Li(s) + 1 I₂(s)   E = _____ V

(d) 1 Mn²⁺(aq) + 1 Pb(s) --> 1 Mn(s) + 1 Pb²⁺(aq)   E = _____ V

Aqueous silver nitrate reacts with aqueous lead (IV) acetate. Calculate the grams of each product formed, starting witb 2.001g of silver nitrate.

Bonding and Molecular Geometry

Pre-Laboratory Question

1. Most elements exist as components of compounds rather than in a free state. Explain why.

2. Use colored pencils to lightly shade each element in the Periodic Table of Electronegativity Values. Color 1 Color 2 Color 3 Color 4 0 – 0.9 1.0 – 1.9 2.0 – 2.9 3.0 – 4.0   Laboratory Questions

1. How does electronegativity influence the bond character between two elements?

2. Describe the conditions that make covalent compounds polar.

3. List the advantages of each type of model and the information that it provides and then list the limitations of that model. Molecular Formula Structural Formula Condensed Structural Formula Skeletal Model Ball-and-Stick Model Space-Filling Model

4. Both the alkene C4H8 and the alkyne C4H6 have rigid bond structures. However, C4H8 can form three isomers, whereas C4H6 can form only two isomers. Why is this so?  

5. Are these molecules isomers? Why or why not?

6. Which of the following molecules are geometric isomers, and which are structural isomers? Which molecule is in the trans position and which is in the cis position?

7. The skeletal model of benzene is often drawn like this:

Hydrogen Sulfide decomposes according to the following reaction for which Kc= 9.30 x 10^-8 at 700 degrees C.

2H2S (g) makes 2H2 (g) + S2(g)

If .43 mol H2S is placed in a 3 L container what is the equilibrium concentration of H2 (g) at 700 degrees C?

Ammonium nitrate is one of the most important nitrogenous fertilizers. Its purity can be determined by reacting this ammonium nitrate with Ba(OH)2. During an experiment 0.4082 g fertilizer powder was just converted by adding 24.42 ml 0.1023 M Ba(OH)2 solution. How much % ammonium nitrate is in this fertilizer?

Please explain how the following two combustion (burning) reactions appear to disobey the law of conservation of Mass: a When a diamond is burned, the mass that remains is zero. B. When a piece of wood is burned, the leftover ashes weight less than the wood. Upon further investigation, it is noted that CO2 is vented off from both reactions. With this additional information, state how you can prove the diamond is made of pure carbon ans yet the wood is not.

Balance the following reactions and indicate which of the six types of chemical reaction are being represented. Assume that all reactions “take place.”    Remember: you want the simplest ratio of coefficients.

1)              ____ NaBr + ____ Ca(OH)₂ à ___ CaBr₂ + ____ NaOH

Type of reaction: _____________________________

2)              ____ NH₃+ ____ H₂SO₄ à ____ (NH₄)₂SO₄

Type of reaction: _____________________________

3)              ____ C₅H₉O + ____ O₂ à ____ CO₂ + ____ H₂O

Type of reaction: _____________________________

4)              ____ Pb + ____ H₃PO₄ à ____ H₂ + ____ Pb₃(PO₄)₂

Type of reaction: _____________________________

5)              ____ Li₃N + ____ NH₄NO₃ à ___ LiNO₃ + _____     Ammonium nitride (Write correct formula, balance)

                                 Type of reaction: _____________________________

6)              ____ HBr + ___ Al(OH)₃ à ___ H­₂O + _____            Aluminum bride (Write correct formula, balance)

Type of reaction: _____________________________

7)          ___ N₂H₄ +   ___ H₂O₂    à ___N₂ + _____ H₂O
                                                                                                                                   Type of reaction: _______________________

8)      ______P₄ +   _____O₂   à    ____               Diphosphorus trioxide      (Write correct formula, balance)    
                                                                                                           Type of reaction _________________________

9)     _____ Fe      +    ____O₂ -à   ________       Iron (III) oxide) (Write correct formula, balance)

Consider the following hypothetical reaction which could occur between a cyclic haloalkane and magnesium hydride: C10H14Cl6 + Mg2H4 → C10H22Cl2 + Mg2Cl4 calculate the atom economy of this reaction assuming that C10H22CL2 is the desired product

What are the effective buffering ranges of MOPS (3-(N-morpholino)propanesulfonic acid) and SHS (sodium hydrogen succinate)? The Nitrogen atom of MOPS can be protonated (pKa=7.2). The carboxyl group of SHS can be ionized (pKa=5.5).Calculate the ratio of basic to acidic species for each buffer at pH 6.5.