In an experiment reported in the scientific literature, male cockroaches were made to run at different speeds on a miniature treadmill while their oxygen consumption was measured. In one hour the average cockroach running at 0.08km/hr consumed 0.8 mL of O2 at 1 atm pressure and 24 ?C per gram of insect weight.
a)
How many moles of O2 would be consumed in 1 hr by a 5.4?g cockroach moving at this speed?
b)
This same cockroach is caught by a child and placed in a 1-qt fruit jar with a tight lid. Assuming the same level of continuous activity as in the research, will the cockroach consume more than 20% of the available O2 in a 48-hr period? (Air is 21 mol percent O2)
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A.
A mixture of carbon dioxide and argon gases, in a 7.78 L flask at 41 °C, contains 12.9 grams of carbon dioxide and 11.9 grams of argon. The partial pressure of argon in the flask is__atm and the total pressure in the flask is __atm.
B.
A mixture of carbon dioxide and
helium gases is maintained in a
5.92 L flask at a pressure of
2.30 atm and a temperature of 88
°C. If the gas mixture contains 14.1 grams of
carbon dioxide, the number of grams of
helium in the mixture is __g.
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What is the pH in a titration of 125 mL of 0.45 F sulfurous acid (H2SO3) with a 1.23 M solution of sodium hydroxide before any base is added?
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An unknown solid is entirely soluble in water. On addition of dilute HCl, a precipitate forms. After the precipitate is filtered off, the pH is adjusted to about 1 and H2S is bubbled in; a precipitate again forms. After filtering off this precipitate, the pH is adjusted to 8 and H2S is again added; no precipitate forms. No precipitate forms upon addition of (NH4)2HPO4. The remaining solution shows a yellow color in a flame test. which might be present, might be absent, definitely absent?
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You have a stock of a DNA solution at 1.2mg/ml, the DNA fragment being 980bp in length. How do you prepare a dilution of this DNA that has a concentration of 0.5uM ?
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Some of the reactions for coal gasification are as follows:
Reaction 1: C(s) + H2O(g) « CO(g) + H2(g) ΔHo = 131.3 kJ/mol
Reaction 2: CO(g) + H2O(g) «CO2(g) + H2(g) ΔHo = -41.2 kJ/mol
Reaction 3: CO(g) + 3H2(g) O(g) « H2O(g) + CH4(g) ΔHo = -205.9 kJ/mol
1.Write the equilibrium constant expression for reaction 3.
2. For all three reactions, predict the way the equilibrium will shift in response to an decrease in pressure. EXPLAIN.
3. For all three reactions, predict the direction in which each equilibrium shifts in response to an increase in reaction volume. EXPLAIN.
4a. Write the ionization of HNO3(aq) using Bronsted-Lowry definition. Identify conjugate acid/base pairs.
b. Find the pH of a .10 M HNO3(aq) solution.
5a. Write the ionization of HClO2(aq) using Bronsted-Lowry definition. Identify conjugate acid/base pairs.
b. Find the pH of a .10 M HClO2 (aq). Ka=1.2 x 10-2.
6. Explain why you set up your calculation the way you did in questions 4 and 5.
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5. The formation constant of the silver-ethylenediamine complex, Ag(NH2CH2 CH2NH2)+, is 5.0 x 104. Calculate the concentration of Ag+ in equilibrium with a 0.10 M solution of the complex. (Assume no higher order complexes).
6. What would be the concentration of Ag+ in (problem 5) if the solution contained also 0.10 M ethylene diamine (NH2CH2 CH2NH2).
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What is concentration of sodium nitrate if 25.5 g of sodium carbonate (MM = 105.99 g/mol) are added to a 500 mL of a 2.50 M iron (III) nitrate solution? Assume to change in volume and don't include units in your answer.
3Na2CO3 (s) + 2Fe(NO3)3 (aq) → Fe2(CO3)3 (s) + 6NaNO3 (aq)
M NaNO3
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|
1) C2H6 (g) -----> C2H4 (g) + H2 (g) ΔH1 = ? 2) C2H6 (g) + 3.5O2 (g) -----> 2CO2 (g) + 3H2O (l) ΔH2 = -1558 kJ/mo 3) C2H4 (g) + 3O2 (g) -----> 2CO2 (g) + 2H2O (l) ΔH3 = -1408 kJ/mol 4) 2H2O (l) -----> 2H2 (g) + O2 (g) ΔH4 = 568 kJ/mol A: Calculate ΔHrxn for reaction (1) based on the given data. Is this reaction endothermic or exothermic? B: How much heat is transferred between the system and the surroundings when 25 grams of ethane (C2H6) decomposes to produce ethylene (C2H4) and hydrogen gas? Is energy is released or absorbed by the system? *** Hint: You will need to calculate ΔH1 and use this value in your calculations to solve for this problem. *** |
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In a practical session, Hubert was asked to prepare potassium peroxide, K2O2 (s). He measured 3.910 g of potassium metal and burnt it in a container of oxygen gas with a mass of 2.560 g.
a) Write a chemical equation with state symbols for the reaction between potassium and oxygen.
b) Deduce which reactant, potassium or oxygen, is limiting.
c) Calculate the amount, in gram, of K2O2 (s) produced in the reaction.
d) It was found that the mass of K2O2 (s) obtained in the experiment was 3.609g. Calculate the percentage yield of K2O2 (s).
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A 25.0 mL sample of 0.100 M HC2H3O2 (Ka = 1.8 x 10^-5) is titrated with a 0.100 M NaOH solution. What is the pH after the addition of 12.5 mL of NaOH?
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1. Instrumentation is a key aspect of chemistry and specifically spectroscopy for organic chemistry. Why is spectroscopy the preferred technique in your opinion? How does this make the field of organic chemistry possible? In regards to mass spectra why is this technique so useful? Why is it so versatile with the various detectors it can be coupled with?
2. Studying about chemical separation techniques how do you see chemical separations in everyday life? How do those separations take place and why are they important? What other chemistry and physics principles do we take advantage of with all separations and why does that matter to us as organic chemist? Why does it matter to you and future or current career goals?
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