Saturday

January 31, 2015

January 31, 2015

Total # Posts: 1,032

**(19) Chemistry - Science (Dr. Bob222)**

Good morning, Could you please let me know how did you calculated K for answer D and C. Thank you.
*May 8, 2014*

**(19) Chemistry - Science (Dr. Bob222)**

Use the following information to answer this question: Cu+(aq) + e- → Cu(s) E° = 0.521V Cu2+ (aq) + e- → Cu+ (aq) E° = 0.153 V. Given these half cell reactions, an aqueous solution of Cu+ ion in the absence of O2(g) : A. will be thermodynamically stable B. ...
*May 8, 2014*

**(11) Chemistry - Science (Dr. Bob222)**

Yes, A! Thank you for making it easy to understand.
*May 7, 2014*

**(11) Chemistry - Science (Dr. Bob222)**

The correct answer is A, which I got it right, but I was torn between A & B. could you please explain why B is incorrect. Thank you.
*May 7, 2014*

**(11) Chemistry - Science (Dr. Bob222)**

In the following hypothetical reaction A + B → C + D, the equilibrium constant, Keq is less than 1.0 at 25°C and decreases by 35% on changing the temperature to 45°C. What must be true according to this information? A. The ΔH° for the reaction is ...
*May 7, 2014*

**Chemistry - Science (Dr. Bob222)**

Thank you!
*May 7, 2014*

**Chemistry - Science (Dr. Bob222)**

Hello, how are you? The correct answer to this Q is E. but I have chosen B. Could you please explain why all of them cannot be true? Thank you
*May 7, 2014*

**Chemistry - Science (Dr. Bob222)**

The following reaction has a positive value of ΔG°. 2H2O(g) → 2H2(g) + O2(g) Which of the following statements must be true? A. The reaction is slow. B. The reaction will not occur. That is, when H2O(g) is introduced into a flask, no O2 or H2 will form even over...
*May 7, 2014*

**(5) Chemistry - Science (Dr. Bob222)**

aha very interesting, thank you so much for this detailed explanation, now I get it.
*May 6, 2014*

**(5) Chemistry - Science (Dr. Bob222)**

Also, could you tell me please how you have solved for X?
*May 6, 2014*

**(5) Chemistry - Science (Dr. Bob222)**

P.S. I just found out that our calculation were right all along for Zn/Cu cell problem... indeed the answer is 1.09V =) Thank you!
*May 6, 2014*

**(5) Chemistry - Science (Dr. Bob222)**

This is a beautiful way of thinking, thank you for sharing. The problem is that at the test I am not given the Ka value for the acid. I solved it this way: I used HH equation, then since we are dealing with the same acid the value of Ka would not change (i thought of it as ...
*May 6, 2014*

**(5) Chemistry - Science (Dr. Bob222)**

Consider a buffer made from 0.13 M sodium acetate and 0.10 M acetic acid in 1L. What amount of KOH must be added to cause an increase of the pH by 0.14? A) 0.048 mol B) 0.038 mol C) 0.028 mol D) 0.018 mol E) 0.008 mol
*May 6, 2014*

**Chemistry - Science (Dr. Bob222)**

Ammonia is a weak base with a Kb of 1.8 x 10-5. A 100.0 mL sample of 0.13 M aqueous solution of ammonia (NH3) is mixed with 87 mL of 0.15 M solution of the strong acid HCl, calculate the pH of the final solution. A) 2.9 B) 11.1 C) 8.8 D) 5.2 E) None of the above
*May 6, 2014*

**Chemistry - Science (Dr. Bob222)**

Thank you! I finally have solved it
*May 6, 2014*

**Chemistry - Science (Dr. Bob222)**

the correct answer is 5.2 mmol; however, I get lost in the calculations. It seems easy to solve: I have pH, pKb, and HH eq, but then I get stuck to derive x correctly
*May 6, 2014*

**Chemistry - Science (Dr. Bob222)**

How many mmol ( millimoles) of HCl must be added to 130.0 mL of a 0.40M solution of methyl amine (pKb = 3.36) to give a buffer having a pH of 11.59? Thank you for your help!
*May 6, 2014*

**Chemistry - Science (Dr. Bob222)**

Posted by Ana on Saturday, May 3, 2014 at 11:23am. A zinc-copper battery is constructed as follows (standard reduction potentials given below): Zn | Zn2+ (0.10 M) || Cu2+ (2.50 M) | Cu Zn2+ + 2 e- → Zn(s) Eº = -0.76 V Cu2+ + 2 e- → Cu(s) Eº = 0.34 V The ...
*May 5, 2014*

**Math**

If a navigation error puts a plane 2 degrees off course, how far off course is the plane after flying 121 miles? Round to the nearest tenth of a mile. Just explain how to solve, please.
*May 5, 2014*

**Math**

A boat travels 74 miles on a course with direction 34 degrees and then changes its course to travel 58 miles at 53 degrees. How far north and how far east has the boat traveled on its 132-mile trip? A 87.7 miles east and 44.3 miles north B 35.7 miles east and 96.3 miles north ...
*May 5, 2014*

**Math**

An airplane, after 1 hour in the air, arrives at a point 350 miles south of its departure point. There was a steady wind of exactly 25 mph from the northwest during the entire flight. Which represents the airplane's average air speed?
*May 5, 2014*

**Chemistry - Science (Dr. Bob222)**

thank you!!
*May 3, 2014*

**Chemistry - Science (Dr. Bob222)**

Ammonium metavanadate reacts with sulfur dioxide in acidic solution as follows (hydrogen ions and H2O omitted): xVO3^–^ + ySO2 → xVO^2+^ + ySO4^2–^ What is the ratio of x : y? A. 1 : 1 B. 1 : 2 C. 2 : 1 D. 1 : 3 E. 3 : 1
*May 3, 2014*

**Chemistry - Science (Dr. Bob222)**

Thank you for such a great response! You are a legend!
*May 3, 2014*

**Chemistry - Science (Dr. Bob222)**

the correct answer is D, but i am confused on the rational here. Not sure what the professor wants me to understand here, the concept behind...
*May 3, 2014*

**Chemistry - Science (Dr. Bob222)**

Use the following information to answer this question: Cu+(aq) + e- → Cu(s) E° = 0.521V Cu2+ (aq) + e- → Cu+ (aq) E° = 0.153 V. Given these half cell reactions, an aqueous solution of Cu+ ion in the absence of O2(g) : A. will be thermodynamically stable B. ...
*May 3, 2014*

**chemistry - Science**

Disregard of 1M solution, it's a typo. The volume of 1.00L is relevant
*May 3, 2014*

**chemistry - Science **

A zinc-copper battery is constructed as follows (standard reduction potentials given below): Zn | Zn2+ (0.10 M) || Cu2+ (2.50 M) | Cu Zn2+ + 2 e- → Zn(s) Eº = -0.76 V Cu2+ + 2 e- → Cu(s) Eº = 0.34 V The mass of each electrode is 200 g. Each half-cell ...
*May 3, 2014*

**chemistry - Science **

A zinc-copper battery is constructed as follows (standard reduction potentials given below): Zn | Zn2+ (0.10 M) || Cu2+ (2.50 M) | Cu Zn2+ + 2 e- → Zn(s) Eº = -0.76 V Cu2+ + 2 e- → Cu(s) Eº = 0.34 V The mass of each electrode is 200 g. Each half-cell ...
*May 3, 2014*

**Chemistry - Science **

A fuel cell designed to react grain alcohol with oxygen has the following net reaction: C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l) The maximum work that 1 mol of alcohol can yield by this process is 1320 kJ. What is the theoretical maximum voltage this cell can achieve?
*May 3, 2014*

**chemistry - (Dr. Bob222)**

Thank you so much! This makes much more sense now. Indeed a great tool to know
*April 21, 2014*

**chemistry - (Dr. Bob222)**

Thank you very much! The formula is very useful,but if it's no trouble for you could you please explain the concept?
*April 21, 2014*

**chemistry - (Dr. Bob222)**

A student attempted to synthesize malonic acid which has a molecular weight of 104 g/mol by the same method used to synthesize aspirin. A titration was performed to find the equivalent weight. 0.125 g of malonic acid product was used for a titration that required 24 mL of 0.10...
*April 21, 2014*

**College Chemistry (DrBob222)**

Thank you! You are legendary!
*April 16, 2014*

**College Chemistry (DrBob222)**

The decomposition of HCO2H follows first-order kinetics. HCO2H(g) CO2(g) + H2(g) The half-life for the reaction at a certain temperature is 44 seconds. How many seconds are needed for the formic acid concentration to decrease by 73%?
*April 16, 2014*

**chemistry - (Dr. Bob222)**

No, they did not provide any reaction for this problem. If I'll find the solution, I'll post it here. Thank you for your help.
*April 16, 2014*

**chemistry - (Dr. Bob222)**

I did that and but I got 1.52 mol/L rather 0.97 (as the answer key provides it)
*April 16, 2014*

**chemistry - (Dr. Bob222)**

The rate constant for a second order reaction has the value of 2.5 x 10–3 L·mol–1·s–1. If the initial concentration of reactant is 3.5 mol·L-1, what will be the molar concentration of the reactant after 2.5 minutes?
*April 16, 2014*

**Chemistry - Science (Dr. Bob222)**

I have calculated K1 and K2 by dividing initial rate to initial concentration [A2], and I solved for Ea but for some reason I don't get the right answer, (which is 10.2KJ)
*April 16, 2014*

**Chemistry - Science (Dr. Bob222)**

Consider the kinetic data given in the table below for the first order reaction: What is the value of the activation energy? A_2_--> 2A Expt. Initial [A2] Temp. Initial Rate mol/L (°C) [A2]·s–1 1 0.10 100 1.2 x 10–3 2 0.20 200 4.8 x 10–3 3 0.15 ? 4...
*April 16, 2014*

**Chemistry - Science (Dr. Bob222)**

Consider the kinetic data given in the table below for the first order reaction: What is the value of the activation energy? A_2_--> 2A Expt. Initial [A2] Temp. Initial Rate mol/L (°C) [A2]·s–1 1 0.10 100 1.2 x 10–3 2 0.20 200 4.8 x 10–3 3 0.15 ? 4...
*April 16, 2014*

**chemistry**

a 0.0500 mol sample of a nutrient substance is burned in a bomb calorimeter containing 2.00 x 10^2g H2O. If the formula weight of this nutrient substance is 114g/mol, what is the fuel value (in nutrient Cal) if the temperature of the water increased 5.70C
*April 15, 2014*

**Math**

Use synthetic division to determine which pair of integers provide both a lower and an upper bound for the zeros of f(x)= x^5-2x^4-25x^3+50x^2+144x-290 PLEASE SHOW WORK!!!
*April 9, 2014*

**Subtracting Fractions with like Denominators**

If Lori's neighbor gave her sixths eighths cup of milk, would she then have enough milk to make her 2 pancakes?
*April 8, 2014*

**french **

Do this sentence is direct or indirect je vais voir mes cousins
*March 26, 2014*

**Physics**

if you throw a 0.2 kg ball straight up at 8 m/s how high will it go
*March 23, 2014*

**physics **

What are the principles behind seatbelts and air bags that make passengers safer in a collision?
*March 23, 2014*

**physics **

If a motorboat travels 25km/h towards the sea, down a river whose velocity is 4km/h what is the boats velocity related to the shore? A, 21 km/h B, 29km/h C, 25 km/h D, 4 km/h
*March 21, 2014*

**physics**

if an airplane is traveling at 550 km/h into a head wind with a velocity of 40km/h what is the airplanes velocity relative to the ground
*March 21, 2014*

**Physics**

If a motorboat travels 25km/h towards the sea, down a river whose velocity is 4km/h what is the boats velocity related to the shore?
*March 21, 2014*

**Chemistry**

How many copper atoms are in a pure copper statue with a mass of 139kg{\rm kg}
*March 5, 2014*

**Chemistry**

Iron ores have different amounts of iron per kilogram of ore. Calculate the mass percent composition of iron for each iron ore: Fe2O3{\rm Fe_2O_3} (hematite), Fe3O4{\rm Fe_3O_4} (magnetite), FeCO3{\rm FeCO_3} (siderite).
*March 5, 2014*

**Chemistry**

Citric acid, the compound responsible for the sour taste of lemons, has the following elemental composition: C{\rm C}, 37.51%\%; H{\rm H}, 4.20%\%; O{\rm O}, 58.29%\%.Calculate the empirical formula of citric acid
*March 5, 2014*

**statistics**

Suppose a manufacturer claims that each family-size bag of pretzels sold weighs 12 ounces on average with a standard deviation of 0.8 ounces. A consumer's group decides to test this claim. If a simple random sample of 49 bags of pretzels gives a sample mean of 11.8 ounces...
*February 25, 2014*

**chemistryyyy**

(a) What is the pH of a 6.1 ✕ 10-5 M Ca(OH)2 solution? (b) What is the H3O+ concentration of the solution? I already know the answer to part A, I just don't understand how you could use that information to find the concentration of H30+ when its not in the ionic ...
*February 23, 2014*

**chemistryyyy**

Thanks! I got part A but how are you supposed to know the concentration of H30+ if its not in the equation?
*February 23, 2014*

**chemistryyyy**

a. What is the pH of a 6.1 ✕ 10-5 M Ca(OH)2 solution? b. What is the H3O+ concentration of the solution? I just cant figure out the ionic equation.
*February 23, 2014*

**Physics**

Canadian geese migrate essentially along a north-south direction for well over a thousand kilometers in some cases, traveling at speeds up to about 100 km/h. If one such bird is flying at 100 km/h relative to the air, but there is a 38.0km/h wind blowing from west to east. a) ...
*February 19, 2014*

**Physics**

A canoe has a velocity of 0.410m/s southeast relative to the earth. The canoe is on a river that is flowing at 0.510m/s east relative to the earth. Find the magnitude of the velocity v⃗ c/r of the canoe relative to the river
*February 19, 2014*

**Algebra 2**

A ball is dropped from 400 ft what is the height of the ball on the 6th bounce? 1 bounce =280 ft 2 bounce= 196 ft 3 bounce = 137.2 How do I figure this out?
*February 6, 2014*

**Biology**

what is independent variable definition?
*February 5, 2014*

**english **

Please HELP Type the word that the underlined phrase modifies or renames. Store the records OF PAYMENTS in the file cabinet. Question 24.. Type the word that the underlined phrase modifies or renames. The house, AN OLD FASHIONED COTTAGE SURROUNDED BY CREPE MYRTLESs, was charming.
*January 8, 2014*

**chemistry**

Acetic acid (CH3CO2H) is a weak acid. As a result, a solution of sodium acetate (NaCH3CO2) will be _____.
*January 6, 2014*

**Math**

(1) 8/1 divided (-3 2/5) My answer is 68/1 (2) 3 2/3 divided by -8 6/7 answer 682/21 3) 41/5 x -8/5 =32/25 Please I need help i'm so confused please show work so I can understand these other 27 problems that i have to complete. Thank you Ms. Sue
*December 10, 2013*

**Compters**

The major reason for the predominance of the PCI bus in the latest models of PCs is that A. the size and form factor make it easy to package. B. it's exclusively manufactured in the USA. C. the technology was released as open source. D. it uses ASSEMBLER language commands.
*December 9, 2013*

**Math**

If x over three minus y over two= negative three. Which statement best explains the value of y changes each time x is increased by one unit? A. The value of y increase by three over two units. B. The value of y increase by two over three units. C. The value of y decrease by ...
*November 21, 2013*

**algebra**

200<d<260
*November 1, 2013*

**Science**

How is Earth like a system?
*October 25, 2013*

**french**

Tu viens d'ou? Comment est CE que le Prof skie? Ou est-CE que tu vas? les crêpe coutent combines? Vous allez a l' Ecole, n'est CE pas?Avec qui est- CE que tu joues au foot? Tu es le professeur match the question question with the letter appropriate answer....
*October 22, 2013*

**french**

Match the question with the letter of the appropriate answer pourquoi est - CE que tu e' tudies le francais
*October 22, 2013*

**math**

powers and exponents
*September 7, 2013*

**math**

can***
*August 28, 2013*

**math**

i dont understand, csn you explain it to me
*August 28, 2013*

**psychology**

In the brain, most excitatory communication in synapses occurs by way of glutamate and most inhibitory communication occurs by way of gamma-aminobutyric acid. In general terms, describe what the other neurotransmitters do.
*July 30, 2013*

**calculus**

A cooling tower for a nuclear reactor is to be constructed in the shape of a hyperboloid of one sheet. The diameter at the base is 260 m and the minimum diameter, 500 m above the base, is 200 m. Find an equation for the tower. (Assume the center is at the origin with axis the ...
*July 8, 2013*

**calculus**

A cooling tower for a nuclear reactor is to be constructed in the shape of a hyperboloid of one sheet. The diameter at the base is 260 m and the minimum diameter, 500 m above the base, is 200 m. Find an equation for the tower. (Assume the center is at the origin with axis the ...
*July 8, 2013*

**algebra **

(3x^2-2x-1) - (5x^2+4x+2)
*June 3, 2013*

**algebra**

I think your wrong A=lxW w=x l=2x+1 So it should be something like A=( ) ( ) and that's the part I dont understand
*June 3, 2013*

**chemistry**

18.5g Al is submerged in 20.2g of water with a total temperature of 27°C. How much energy in joules is absorbed by the Al if the temperature changes to 32°C ?
*May 28, 2013*

**Statistics**

X Y 0 23 2 27 2.3 29 4.1 32 5 35 What is the correlation for this data set? 10) Find the regression line for this data set.
*May 25, 2013*

**math**

what is a data
*May 9, 2013*

**math**

finding the average
*May 9, 2013*

**math**

finding the mean
*May 9, 2013*

**Algebra**

Evaluate the determinant of the matrix. [-4 5 6 0 4 4 -2 -5 4]
*April 19, 2013*

**Algebra 2 variables**

Find the values of the variables. [-12 -w^2] = [2k -81] [2f 3] [-4 3] Show your work?
*April 19, 2013*

**Algebra 2**

Find the sum [1 4] [0 0] [0 3] + [0 0] A - [1 4] [0 3] B - undefined C - [0 0] [0 0] D - [1 0] [4 3]
*April 19, 2013*

**math**

evaluate the expressions below and leave them in radical form. 1. sin(pie symbol/6)csc(pie symbol/6) 2. sec(pie symbol/3)cos(pie symbol/3)+tan(pie symbol/3)cot(pie symbol/3)
*March 30, 2013*

**science**

thank you.
*March 27, 2013*

**science**

plz delete after 20 minutes of answering
*March 27, 2013*

**algebra**

A store mixes kenyan coffee worht $12 per kilogram and turkish coffee worth $16 per kilogram the mixture is to sell for $14 per kilogram how much of each should be used to make a 348-kilogram mixture?
*March 18, 2013*

**Spanish**

how old am I
*February 17, 2013*

**Science**

How do you find the hours of daylight ?
*January 30, 2013*

**Algebra 2 **

The Formula s= sqrt 30fd can be estimated the speed of s, in miles per hour that a car is traveling when it goes into a skid, where f is the coefficient of friction and d is the length of the skid marks in feet. Kody skids to a stop on a street with a speed limit of 35 mi/h. ...
*January 21, 2013*

**4th grade math**

you find a common denominator, which is 4 in your case, and because you multiply 2 by 2 you have to multiply 41 by 2 as well, so you get 82/4-1/4, ok or do you need more help?
*January 20, 2013*

**math**

In the xy-coordinate plane, the distznce between point B(15,7) and point A(x,15) is 17. What is one possible value of x?
*January 19, 2013*

**science project**

I'm trying to find information on does lung capacity depend on height
*January 18, 2013*

**Reading/Language Arts**

Did i rewrite my paragraph right.Also thank you for your help
*January 12, 2013*

**Reading/Language Arts**

the energy we get to heat up the house and run our appliances is a energy solar panel.And it has an adverse affect on it do to the heavy snow fall.The apparatus does not generate enough energy do to lack of sunlight. And we need that energy to power our house for heat hot ...
*January 12, 2013*

**Reading/Language Arts**

The energy we get to heat up our house and run our appliances. Is a solar panel and is a necessity to live an everyday life. Do to a adverse affect on the solar panel caused by to much snow. The apparatus does not get enough sunlight to generate electricity. That the house ...
*January 12, 2013*

**Reading/Language Arts**

I,m writing a paragraph about using resources responsibly.And I have to use three vocabulary words adverse,generate,apparatus. And this is what I wrote. The energy to the house I live in has had a adverse affect.Do to the apparatus not getting enough sunlight to generate all ...
*January 12, 2013*

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