Octane, C₈H₁₈, a primary constituent of gasoline, burns in air:

C₈H₁₈(ℓ) + 12 1/2 O₂(g) → 8 CO₂(g) + 9 H₂O(ℓ)

A 1.00-g sample of octane is burned in a constant volume calorimeter. The calorimeter is in an insulated container with 1.20 kg of water. The temperature of the water and the bomb rises from 25.00 °C (298.15 K) to 33.21 °C (306.36 K). The heat required to raise the bomb’s temperature (its heat capacity), C_bomb, is 837 J/K. The specific heat of water is 4.184 J/g∙K. What is the heat of combustion per gram of octane? What is the heat of combustion per mole of octane?

kJ/g

kJ/mol

You need to be able to get an answer of 2.14 x 10^-7 M for part c.

A lead ion-selective electrode measured a potential of -33.9 mV when immersed in 50.00 mL of water from a polluted stream. Upon the addition of 0.5 mL          of a 0.105 mM solution of Pb(NO₃)₂ the potential changed to -11.2 mV.

a)  Write an equation for the response of this electrode, ignoring the response of any other elements (i.e., we will assume selectivity coefficients for non-lead species are all zero) (4 points).

b) Assuming β = 1 in the above equation, write expressions for the response of the electrode to the original sample and to the spiked sample (6 points).

c) Solve the equations you wrote in (b) to find [Pb²⁺] in the original sample (6 points).

Complete and balance the following redox reaction in acidic solution

a) ReO4- (aq) +IO- (aq) --> IO3- (aq) + Re(s)

b) Pb^2+ (aq) + IO3- (aq) --> PbO2(s) + I2(s)

c) IO3- (aq) + Re(s) --> ReO4- (aq) +IO- (aq)

I'm not understanding quite how to do this type of problem. The problem states: What is the enthalpy change produced by the reaction of 50.0 g Fe2O3 with 50.0 g Al according to the equation below?

Fe2O3(s) + 2Al(s) => Al2O3(s) + 2Fe(s) Delta H = -851.5 kJ

Please show me how to do this!

1. Three (03) students are planning to run Diels-Alder reactions using maleic anhydride as dienophile and three (03) different dienes (A, B, and C). Student A will be using cyclopenta-1,3-diene (compound A), Student B will be using buta-1,3-diene (compound B) and student C will be using 1,2,3,7,8,8a-hexahydronaphthalene (compound C).

1. Draw the reaction schemes for Student A, Student B and Student C using the above given starting materials (write “NO REACTION” whenever the reaction is impossible).

Student A’s reaction scheme (2 pts)

Student B’s reaction scheme (2 pts)

Student C’s reaction scheme (2 pts)

2. Which of the three reactions would you expect to be the fastest? Why?(2 pts)

3. Student A would have to crack the cycolpentadiene before it can be used, while student B will use the butadiene as purchased; explain why? (4 pts)

(d). Why is maleic anhydride a much better dienophile than ethylene (CH₂=CH₂)? (2 pts)

(e). When producing Diels-Alder adducts using maleic anhydride as the dienophile, why is it important that reagents and apparatus be dry? (2 pts)

(f). Why is Diels-Alder reaction exothermic process? Explain considering bond cleavage and bond formation contribution to the enthalpy change (2 pts)

8- trace elements in the teeth of archeological speciment provides anthropologists with clus about the dite and diseases of ancient people . Porter et al (20020 measured the trace elements strontium from extracted teeth by atomic absorption spectroscopy. A series of solutions were preaperd, each containing 0.750 mg of dissolved tooth enamel. Varying volumes of 100.0 ng/ml Sr stock solution were added to each flask ,and each solution was diluted to a total constant volume of 10.0 ml The final result was a series of flasks containing the following concentration of added Sr.

flask Volume of Sr stock solut. added ,ml concent. of Sr after diluttion ng/ml Blank-concent signal

1 ? 0.00 28.0

2 ? 2.50 34.3

3 ? 5.00 42.8

4 ? 7.50 51.5

5 ? 10.0 58.6

a. suppose 5.00 mg of powdered tooth enamel is dissolved in ultra- pure HNO3 and diluted to 10.0 ml in volumetric glasswear. What volume of this solution must be delivered to each flask , in order to deliver 0.750 mg dissolved enamel to the flask? (show calculations)

b. The Sr standards in the table above were made by delivering volume aliquote of a 100.0 ng/ml Sr stock solution to each 10.0 ml flask . complete the table above to show what volume of Sr stock were added to each flask ,in order to produce the specific concentrations of added Sr?(please show calculations)

c. What type of standardization is being performed here? why is this type of standardization being used , rather that some alternative standardization?

d. Least -squares analysis of the data resulted in the plot shown , where y=3.136x+27.36 and R^2 =0.9973

calculate the concentration of Sr in flask.( show the plot from -10 -5 0 5 10)

e. calculate the Sr content in the original tooth enamel , in units of ppm=micro gram Sr/g enamel. ( please show complete calculation)

Which of the following represents the hydrolysis of the ammonium ion?

9. In the crystal structure of CsCl, the distance between Cs+ and Cl is equal to 3.55 Å (0.355 nm). Calculate density of CsCl (in g/cm3 ).

How many colors are in the visible spectrum?

9) What is a common, high end, reinforcing material for polymer composites used in aircraft?

Please explain in clear words. Thanks

1. Calculate the mass of KHC₈H₄O₄ (molar mass = 204.44g/mol) that reacts with 15mL of NaOH solution in part A.3. Express this mass of KHC₈H₄O₄ to the correct number of significant figures and record the calculation on the report sheet.

2. A 0.204g sample of CO₃^2- antacid is dissolved with 25.0mL of 0.0981M HCl. The hydrochloric acid that is not neutralized by the antacid is titrated to a bromophenol endpoint with 5.83mL OF 0.104M NaOH. Calculate the number of moles of base in the antacid.

In regards to reactivity with sodium metal please confirm my statement that:

***"Primary alcohols react faster/most with Sodium metals, and tertiary alcohols react the slowest". ***

1. Methyl alcohol will react FASTER with sodium metal than 2-propanol. TRUE

2. In order from least reactive to most with sodium metal: tert-butyl alcohol, 2-butanol, 1-butanol. (with respect to their acidity)

Provide a chemical definitation of the following:

1- Equilibrium Constant

2- Le Chatelier princeiple.

3- Dynamic equilibrium

The work function of palladium is 5.22 eVeV.

part A:

What is the minimum frequency of light required to observe the photoelectric effect on PdPd? Express your answer with the appropriate units. Answer: 1.26×10¹⁵ s−1

please help with part B

If light with a 150 nmnm wavelength is absorbed by the surface, what is the velocity of the emitted electrons?

Express your answer with the appropriate units.