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October 25, 2014

Posts by ANDREA


Total # Posts: 690

Chemistry
A p-n junction is to be created by diffusing boron (B) into an n-type silicon wafer with an existing carrier concentration of 1015/cm3. The location of the junction will be 6μm below the surface of the wafer. The surface concentration of boron will be maintained at 1020/...
December 6, 2012

Chemistry
To increase corrosion resistance, chromium is diffused into steel at 980∘ C. If the surface concentration of Cr is maintained constant at 100%, how long will it take (in days) to achieve a Cr concentration of 1.8% at a depth of 0.002 cm below the steel surface? (D0=0.54 ...
December 6, 2012

Chemistry
A p-n junction is obtained at a depth of 3×10−3 cm by diffusion of antimony (Sb) into p-type germanium. What is the acceptor concentration in the bulk Ge, if diffusion was carried out for three hours at 790∘ C? Given: Constant Sb surface concentration is 8&...
December 6, 2012

Chemistry
The Gaussian error function can be approximated for small values of x as erf(x)≈x. Suppose a silicon wafer is exposed to aluminum vapor at 1300∘ C. At what distance (in centimeters) will the concentration of Al be 35% of the surface concentration in 164 hours? ...
December 6, 2012

Chemistry
(a) Certain alloys such as LaNi5 can store hydrogen at room temperature. A plate of LaNi5 containing no hydrogen is placed in a chamber filled with pure hydrogen and maintained at a constant pressure. At what depth from the surface will the concentration of hydrogen be 1/2 the...
December 6, 2012

Chemistry
You wish to remove nitrogen from the near-surface region of a plate of cobalt which is 1.0 cm thick. The plate is placed in a furnace at 417∘ C where an atmosphere of H2 and NH3 reacts with the nitrogen in the cobalt and fixes the surface concentration to 111 ppm (parts ...
December 6, 2012

Chemistry
An undesirable consequence of welding steel by acetylene torch is the rise in hydrogen concentration in the metal. That hydrogen contamination embrittles the steel. The metal is typically subjected to a vacuum heat treatment to restore ductility. A steel part is placed in a ...
December 6, 2012

Chemistry
Carburization" of pure iron (Fe) is carried out at 950∘ C. It is desirable to achieve a carbon content of 0.9% at a depth of 0.1 mm below the surface. A constant supply of carbon at the surface maintains a surface concentration of 1.2%. Assuming the diffusivity of ...
December 6, 2012

geometry
10 and 2 - 3
December 6, 2012

psychology
hello, can you help me try to find research for sigmund freud unconscious mind thank you
December 5, 2012

Physics
There is a door that is 1.0 m wide and can rotate about a vertical axis without friction. The door’s mass is 15 kg and is free to swing open. Someone fires a 10 g bullet at 400 m/s into the exact center of the door, perpendicular to it. Find the angular velocity of the ...
December 2, 2012

Algebra
a helicopter that is 200 meters above the ground descends at a rate of 2 meters per second. The altitude of the helicopter after t seconds is given by h(t)=2000-2t. 1)give the range of this function 2)give the domain of this function.
November 27, 2012

Algebra
Joyce combines 9 atoms of hydrogen and 3 atoms of nitrogen to make 3 molecules of ammonia. write a direct variation equation which relates atoms of hydrogen to atoms of nitrogen. How many nitrogen atoms does Joyce need to form ammonia molecules using 51 hydrogen atoms?
November 27, 2012

Algebra
please help! Noah knows that his friend Ryan uses 2 small chlorine tablets each week to maintain his 10,000 gallon pool: 1)Write a direct variation equation that relates c and g, where c is the number of chlorine talets and g is pool volume in gallons. 2)How many small ...
November 27, 2012

English THE GREAT GATSBY
1. Fitzgerald creates purpose in Chapter 1. What was his purpose and how does he go about doing it? 7. Write a Gatsby-esque sentence. Make it colorful. My sentence is below... does it make sense? Life to some in New York may seem very Gatsbyesque, what with their tall ...
November 26, 2012

Physics
A car moving at 43 km/h skids 16 m with locked brakes. How far will the car skid with locked brakes at 129 km/h?
November 25, 2012

math
rectangle room is 3.75 m by 2.84 m what is the length of the diagonal? how to calcuate?
November 21, 2012

math
rectangle room is 3.75 m by 2.84 m what is the length of the diagonal? how to calcuate?
November 21, 2012

American History
1. Believing that truth is what works for actual real people, Harvard psychologist William James developed the philosophy of (A. pragmatism.) B. social progressivism. C. radical progressivism. D. social idealism. 2. Which of the following was true of Secretary of State William...
November 14, 2012

earth
HELP? Two students are given cubic boxes, measuring 10 cm on a side. Robert puts a single glass marble with a diameter of 10 cm in the box. Susan puts 1,000 1-cm glass marbles in her box. 1.Whose box has more empty space? Explain. 2.Whose box will be heavier? Explain. Can you ...
November 14, 2012

Physics
Water is flowing through a horizontal pipe at a rate 0.2 m3/s. The pipe narrows from a radius of 10 cm to 4 cm. What is the change in pressure?
November 13, 2012

spanish III
These are my directions: Change the present tense verb in the sentence to the preterite tense. Can you help me understand how to do this? These are the Questions(1-5): 1. Voy a estudiar. 2. Vas a dar comida al perro 3. Es un estudiante. 4. Somos aquí. 5. Son có...
November 10, 2012

science- geology
I have to draw a topographical map on poster board of an imaginary island. It must have 2 mountains, 12 MI apart, one with a benchmark of 1510 ft and the other of 1075 ft. We must include 2 streams, one that flows down the larger lake into the ocean, the other must flow in and...
November 7, 2012

math
express the sum of difference in simplest form 1-1/6-11/18=
October 29, 2012

Physics
The pulley system shown in the figure is used to lift a 37 kg crate. Note that one chain connects the upper pulley to the ceiling and a second chain connects the lower pulley to the crate. Assume that the masses of the chains, pulleys, and ropes are negligible and the crate is...
October 25, 2012

Gen Chem
ignition of mgnh4po4*6h2o produces nh3, h2o and magnesium pyrophosphate, Mg2P2O7. complete and balance the equation for this reaction. If 5.00 g of MgNH4PO4*6H2O are ignited, how many grams of Mg2P2O7 would be formed? 2MgNH4PO4*6H2O(g)--->
October 23, 2012

Gen Chem
I got the answer of 249.6 Is that correct? Thanks for your help!
October 23, 2012

Gen Chem
what is the formula weight for CuSO4 5H2O?
October 23, 2012

Gen Chem
epsom salts, household ammonia, and rubbing alcohol are also consumer chemicals that could be used in this experiment. what are the chemical formulas for these substances?
October 22, 2012

Gen Chem
For my chem class I have 3 elements and have to find what they are used for today or an interesting fact. I have looked but I can't really fin anything. My elements are: Cobalt,Thulium, and Roentgenium I found that cobalt is used in money (nickels, quarters, and dimes, but...
October 21, 2012

Chemistry
Balance the equation and write the reaction-quotient expression, Qc. U(s) + F2 (g) <----> UF6 (g)
October 15, 2012

Algebra
How do the solutions of the equation compare to the length of the rectangular object and the x-intercept of the graph? Provide both the solutions and measurement. x^3-10x^2+21x -108 = 0 Length: 9 inches Height: 6 inches Width: 2 inches
October 12, 2012

Algebra II
Can you make sure my Algebra II work is correct? I've done the problems. I just want to make sure I am right. 1. Write an equation of the line with a slope of 5 and a y-intercept of -3. y=5x-3 2. Write the equation of a line that passes through (9, 3) and has a slope of 2/...
October 4, 2012

Break-Even Analysis
Given: Jay Letterman has just (year: 2012) become product manager for Avenir. Avenir is a consumer product with a unit retail price of $1.00. Retail margins on the product are 33%, while wholesalers take a 12% margin. Avenir and its direct competitors sell a total of 20 ...
October 1, 2012

Finance
Given: Jay Letterman has just (year: 2012) become product manager for Avenir. Avenir is a consumer product with a unit retail price of $1.00. Retail margins on the product are 33%, while wholesalers take a 12% margin. Avenir and its direct competitors sell a total of 20 ...
September 29, 2012

Ella Minnow Pea
I read the book Ella Minnow Pea for school... And I actually enjoyed it! But I have to answer some questions about it and I'm not quite sure what I am suppose to be answering. Do you understand these questions better than me? Here they are! Identify the stylistic devices ...
September 26, 2012

us history
I WILL pass that test. And the class was free so no money was wasted.
September 26, 2012

us history
I'm not going to drop the class. And due to some personal issues(No not pregnancy)I am taking online school. They did not issue us books therefore I am going in basically blind. Like I said, I'm trying to get a tutor.
September 26, 2012

us history
Can you help me on this? How consistent were the republican principles applied by Thomas Jefferson and James Madison during their presidencies? How did their policies affect the Federalist Party during Jefferson's and Madison's administrations? I can't find the ...
September 26, 2012

History Help?
How did the compromises made when writing and ratifying the Constitution encourage the development of political factions? Compare and Contrast the effectiveness of Washington's and Adams' presidencies in obeying and promoting the Constitution during their administrations.
September 26, 2012

us history
Evaluate the extent to which the Articles of Confederation were effetive in solving the problems that confronted the new nation. Does anywone know where I can find the answer to this? I have to type a whole page on it so I need a lot of information... please and thank you! No ...
September 26, 2012

AP US History
Well... despite the fact that I am not good at history I did sign up for the class and I AM STICKING WITH IT. I am not going to swtich out. Thank you for your time, however, my descision to stay in the class will not be swayed. I do need help with it however, and I am looking ...
September 26, 2012

AP US History
How did the compromises made when writing and ratifying the Constitution encourage the development of political factions? Compare and Contrast the effectiveness of Washington?s and Adams' presidencies in obeying and promoting the Constitution during their administrations. ...
September 26, 2012

AP US History help?
I will do that. Thank you!
September 26, 2012

AP US History help?
I know this is really long... but I can't figure it out for the life of me. If you don't want to answer the whole question that is fine. I'm greatful for whatever I can get. Also links to websites with the information is also helpful. Thanks!! Directions: Read the ...
September 26, 2012

algebra
Thank you Steve for your help!
September 26, 2012

Stumped at Algebra II
How in the world do you do this? I'm so confused. Thank you all for your time and help... -2 < 2x - 5 < 3
September 26, 2012

algebra
Solve for y, xy + x = -3 How do you do this? I can't seem to come up with the correct answer...
September 26, 2012

algebra
how do i complete the table with 4x-y=5 x: 0 1, 2 and im trying to find 'y'
September 26, 2012

Algebra
solve the linear system using substitution 4x - y=5 4x + 4y= -4 Also by using elimination.
September 25, 2012

Chemistry
How do you convert it to moles of asprin?
September 23, 2012

Chemistry
Aspirin (C9H8O4) is synthesized by the reaction of salicylic acid (C7H6O3) with acetic anhydride, C4H6O3. 2C7H6O3 + C4H6O3 −→ 2C9H8O4 + H2O When 19 g of C7H6O3 and 19 g of C4H6O3 react, which is the limiting reagent?
September 23, 2012

algebra
Damon, thank you so much!! This helped a lot!
September 23, 2012

algebra
Hi, I need some help on my homework. Can you help me? True or False, if False correct the underlined portion. 1) If 3<x, then 3+y<x+y 2)If |w-7|<-3, then w-7>-3 or w-7<3 3) If -4<-2t+6<10, then 2>t+6>-5 4) If |y+8|+2=6, then y+8=+-4* * the "+&...
September 23, 2012

AlgebraII
How do you get the answer for this equation a+2b+(14a-5b)-[6a+6b-(a+4)]
September 19, 2012

physics
which natural phenomenon can describe light as a wave?
September 7, 2012

chemistry
The height of a stack of 5 pennies is 0.72 cm and the radius of the stack is 0.91 cm. The volume in mL of this stack of 5 pennies is...
August 30, 2012

Math
WHERE DO I PUT THE PERENTHESIS TO MAKE THIS STATEMENT TRUE: 18+2*1+3 TO THE SECOND POWER
August 27, 2012

medical billing and coding
Your search for This 82-year-old female was admitted for acute exacerbation of chronic obstructive pulmonary disease. The progress notes indicate that the patient received a transfusion for anemia. The discharge diagnoses state acute exacerbation of chronic obstructive ...
August 24, 2012

chemistry
treatment of a 0.400g sample of impure potassium chloride with an excess of AgNO3 resulted in the formation of 0.733g of AgCl. calculate the percentage of KCl in the sample. show balanced equations in support of your answer
August 15, 2012

math
In a family of 5 children, how many different ways can you have 3 boys and 2 girls?
August 15, 2012

math
Thanks, Steve. I believe we were supposed to convert the 16 inches into centimeters first (which is 40.64 cm, right?) to solve for both V and A and then take our final, not-rounded answer, convert it back into inches, and then round.
August 15, 2012

math
Find the volume and surface area of a right cylinder with radius 7.5 cm and height 16 in. Make sure your final answer is in inches. Round your answer to the nearest hundredth.
August 15, 2012

math
Thank you, Ms. Sue and Vanessa! I thought this might be a trick question, and that perhaps the correct answer was 2 (keeping logs whole).
August 15, 2012

math
Mr Logan can saw 8 logs in 3 hours. How many logs can Mr Logan saw in one hour?
August 15, 2012

medical billing/coding
I need help coding this question. could someone help me. CPT CODE:__________________________ ICD-9-CM CODE:_____________________ Code the following "You've started your first day at Venture Outpatient Surgery Center. OPERATIVE REPORT: Preoperative diagosis: Left flank...
August 3, 2012

medical billing and coding
what are the CPT and ICD-9-CM codes for following question? "this is a pleasant female who comes in with a soft tissue lesion in the left flank over what appeared to be a spigelian hernia site as well. However, it was not reducible and did not appear to be consistent ...
August 2, 2012

Physical Science
1. You are assigned to take care of a patient who is scheduled to undergo a surgical operation. The doctor told you not to allow the patient to eat for twelve hours. How many minutes is the fasting period? 2. What is the density of a rock (in g/cm3) which has a volume of 2.5 ...
June 15, 2012

geometry
If m∠BCD = 60 and m∠DEC = 80, what is the measure of ∠DEF
June 15, 2012

business
ACTUAL DECISION / PREDICTED DECISION A B C A 80 5 12 B 14 60 14 C 10 15 70
June 9, 2012

business
A researcher was given the assignment of predicting which of three actions would be taken by the 280 employees in the Desota plant that was going to be sold to its employees. The alternatives were to: a. Take severance pay and leave the company. b. Stay with the new company ...
June 9, 2012

geometry
a circular cylinder has a base with a radius of 7.5 cm. and a height of 12 cm. a rectangular prism has a square base and height of 8.0 cm. if the cylinder and the prism have equal volumes, what is the length of the base of the prism to the nearest tenth?
May 29, 2012

Algebra
f(x)=x^2-1 ; x = -3, -2, -1, 0, 1, 2, 3 i got 8,3,0,-1,0,3,8 as the answer when i plugged in x. how would i graph these numbers from this function?
May 20, 2012

Econ
Do people living in countries with higher real GDP necessarily have better living standards compared to countries with relatively lower GDP? Give practical example. 2. What measures would better compare the well-being (living standard) for residents of different countries? How...
May 17, 2012

Chemistry
Which of the following pairs of compounds will give a precipitate in a diluted solution?** a) Cu(NO3)2 and Na2CO3 b) KNO3 and NaCl c) MgCl2 and Ba(NO3)2 d) NH4Cl and Al2(SO4)3 A solution contains I-, Br- and OH- ions. If Ag+ is added, what will the precipitate(s) be? a) AgOH b...
May 15, 2012

Chemistry
Acetic acid dissociates/ionizes itself as follows: CH3COOH(aq) ⇔ H+(aq) + CH3COO-(aq) If you add sodium acetate, CH3COONa, to the solution: a) a precipitate will be formed b) more acetic acid will be ionized c) the concentration of hydrogen ions will decrease d) the ...
May 15, 2012

Chemistry
A mixture of lead, magnesium, nitrate and chromate ions are present in a solution. What will the precipitate be?** a) MgPb b) Pb(NO3)2 c) PbCrO4 d) MgCO3
May 15, 2012

Chemistry
Consider the reaction 3X + Y ⇔ 2W + Z. At equilibrium, [X] is 7.0 M, [Y] is 6.0 M, [W] is 5.0 M and [Z] is 7.0 M at 298 K. The value of the equilibrium constant at this temperature is: a) 0.085 b) 0.560 c) 1.800 d) 11.760
May 15, 2012

Chemistry
0.80 mol/L of A and B are mixed. They react very slowly to produce C and D as follows: A(aq) + B(aq) ⇔ C(aq) + 2D(aq) When equilibrium is attained, the concentration of C is 0.60 mol/L and the concentration of A is: a) 0.20 M b) 0.40 M c) 0.60 M d) 0.80 M
May 15, 2012

Chemistry
In the system A(g) + 2B(g) ⇔ 2C(g) + 2D(g) ΔH=21 kJ/mol, it is possible to increase the quantity of C by: a) adding a catalyst b) decreasing the [B] c) increasing the pressure d) increasing the temperature
May 15, 2012

Chemistry
For the following acids: i. CH3COOH ii. HNO2 iii. HCN a) What is the dissociation equation in an aqueous solution? b)Give the KA expression for each of the acids. c)Identify the acid-base pairs.
May 13, 2012

Chemistry
A weak acid solution, HX 0.37 M, has a pH of 3.70. Calculate the acidity constant for this acid.
May 13, 2012

Chemistry
Calculate the volume of Ba(OH)2 0.20 M necessary to neutralize 300.0 mL of H3PO4 0.30 M. (4 marks)
May 13, 2012

chemistry
What is the pH of a solution prepared by dissolving 12.2 g of benzoic acid in enough water to produce a 500 mL solution?
May 13, 2012

Chemistry
Commercial vinegar usually has a concentration of 5%, per volume. a) Calculate the [H3O+] , if the density of acetic acid is 1.051 g/mL. b) Calculate the pH.
May 13, 2012

Chemistry
Calculate the KA of formic acid if 2.3 g of it is dissolved in 1 litre of water to give [H+] of 0.003 M.
May 13, 2012

Chemistry
The equilibrium constant for the following reaction is 7.2 x 10-10. What is the [H+] in a solution 1.0 M of this acid? HCN + H2O --> H3O+ + CN-
May 13, 2012

Chemistry
200 g of CH3COOH are dissolved in enough water to make 1.5 L. What is the molarity of the acetic acid solution?
May 13, 2012

Chemistry
Which of the following contains the highest H3O+ ion concentration? Explain your answer. HCl 0.1 M HCH3CO2 0.1 M
May 13, 2012

Chemistry
a) What is the dissociation equation in an aqueous solution? b)Give the KA expression for each of the acids. Identify the acid-base pairs.
May 13, 2012

Chemistry
Are the reactants or the products favoured in the following reactions? a. CH3COOH with NH3? b. HS- with HCO3-? c. HNO2 with NH3 d. NH4+ with F- e. C6H5COOH with CH3COO- f. H2SO3 with HCO3- g. H2CO3 with SO32- h. H2SO3 with SO32-
May 13, 2012

Chemistry
Classify the following 3 acids in order of increasing acidity: Acid 1:Ka = 8 x 10-6
 Acid 2:Ka = 6 x 10-4
 Acid 3:Ka = 9 x 10-11
May 13, 2012

Math 3rd grade
Fred needs to do quite a few errands. He needs to stop by the cleaners, the post office, the hardware store, and the bank. There are a number of ways he can tackle his list of stops. How many ways can he accomplish his tasks?
April 10, 2012

business
On December 31 of last year, Wolfson Corporation had in inventory 400 units of its products, which cost $21 per unit to produce. During January, the company produced 800 units at a cost of $24 per unit. Assuming that Wolfson Corporation sold 700 units in January, what was the ...
March 20, 2012

business
At the end of January, Mineral Labs had inventory of 725 units, which cost $10 per unit to produce. During February the company produced 650 units at a cost of $14 per unit. If the firm sold 1,000 units in February, what was the cost of goods sold? a. Assume LIFO inventory ...
March 20, 2012

Earth/Space Science
What is one way you can make a difference and decrease the impacts of soil erosion?
March 18, 2012

astronomy
Suppose that the gravitational time dilation on the surface of a star is 1.1. What would be the escape velocity from the star?
March 11, 2012

astonomy
If 100 asteriods, each of diameter of 100 km, were combined into a single object, approximately what would its diameter be?
March 11, 2012

Algebra
I have an input / output machine I need a rule I can use for any value, like 10 or 100 input 1, output 3 input 2, output 6 input 3, output 12 input 4m output 24
March 5, 2012

Chemistry
Hoe Many moles of each reactant are Needed to produce 3.60 x 10^2g CH3OH?
March 5, 2012

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