Popular questions and responses by KC
  1. chemistry

    CH4 + 2O2 ---> CO2 + 2H2O Delta H H2O= -285.8 kJ/mole Delta H CO2= -393.3 kJ/mole What is the standard heat of formation of methane, Delta H CH4, as calculated from the data above

    asked on November 18, 2011
  2. math

    a rabbit climb up a flight of 10 stairs and can only hop 1 or 2 steps each time. he never hops down, only up. How many ways can the rabbit hop up the flight of 10 steps?

    asked on June 7, 2010
  3. chemistry

    Which of the following pairs can be used to prepare a buffer? (select all that can apply) a. HCl/NaCl b. HF/KF c. NH3/NH4Cl d. HNO3/HNO2 e. NaNO2/HNO3 can you also please explain how they form a buffer? thank you

    asked on April 12, 2012
  4. algebra

    a bank teller has 52 $5 and $10 bills in her cash drawer. the value of the bills is $460. how many $5 bills are there?

    asked on April 18, 2012
  5. Algebra

    The width of a rectangle is 1 ft. less than the length. The area is 2ft^2. Find the length and the width.

    asked on March 2, 2008
  6. pre cal 2

    solve the equation 4cos^2x-1=0

    asked on July 24, 2011
  7. Math

    Find an expression for the function. Top half of the circle: x^2+(y-2)^2=4.

    asked on September 10, 2012
  8. Math

    Use the Intermediate Value Theorem to show that there is a root of the given equation in the specified interval. cos x = x. How do I begin this problem? According to the theorem, a=0, b=1 and N=x?

    asked on September 2, 2012
  9. Algebra

    What does it mean to refer a 20-in television set or a 25-in TV? Such units refer to the diagonal of the screen. A 20-in set also has a width of 16 inches. What is the height?

    asked on March 7, 2008
  10. Trig

    Solve the equation on the interval 0 less than or equal 0 < 2pi. 1. sec 30/2 = -2 2. cos(20 - pi/2) = -1 3. tan(0/2 + pi/3) = 1

    asked on September 25, 2007
  11. Math

    Greta said that the product of two prime numbers must also be a prime number. Joan disagreed. Who is correct?

    asked on December 6, 2011
  12. Math

    A class has 12 students. In how many different ways can the students be put into lab groups consisting of 3 students in each group. The answer in the book is 369600. But I do not understand how they got this answer.

    asked on January 26, 2011
  13. physical chemistry

    Calculate the equilibrium constant (K) for the ammonia synthesis reaction at 25°C and show how K is related to the partial pressures of the species at equilibrium. Consider that the overall pressure is low enough for the gases to be treated as perfect.

    asked on November 10, 2010
  14. Science

    Three statements that define all living things in terms of cells That's not even a complete sentence or question. I searched Google under the key words "living cells define" to get these possible sources: http://www.answers.com/topic/cell

    asked on October 10, 2006
  15. physics

    A particle with charge 7 µC is located on the x-axis at the point 4 cm , and a second particle with charge 7 µC is placed on the x-axis at 6 cm . −10−8 −6 −4 −2 2 4 6 8 10 7 µ C 7 µ C 8 µ C x → (cm) What is the magnitude of the total

    asked on April 8, 2020
  16. Chemistry

    What is the percent by mass of NaHCO3 and KCl in the mixture.

    asked on February 15, 2015
  17. chemistry

    A buffer solution is made by dissolving 0.45 moles of a weak acid (HA) and 0.13 moles of KOH into 760 mL of solution. What is the pH of this buffer? Ka = 3.3 × 10−6 for HA.

    asked on February 2, 2015
  18. us history

    In many ways after the divisiveness and devastation of the Civil War, the United States searched for order economically, politically, geographically, socially and racially. Select one of these areas, or suggest another, and make a case for the reasons why

    asked on December 5, 2012
  19. math

    Jamal buys 59 stickers. Stickers come in packs of 5 or 8. How many packs of 5 stickers does Jamal buy? 8 stickers?

    asked on March 7, 2012
  20. geometry

    If FD=4x-27, and SG is congruent to FD and SG=2x-3, Then whais the length of SG?

    asked on November 14, 2011
  21. chemistry

    Suppose the following: HO-C(H2)-C(H2)-OH + 2 HI --> I-C(H2)-C(H2)-I + water How many mL of the first compound* are needed to react with 9.3 grams of HI? (The density of the first compound is A = 1.11 g/mL) *by first compound, i mean HO-C(H2)-C(H2)-OH

    asked on September 2, 2011
  22. pre cal 2

    find the exact solutions in the interval [0,2pi), sin4x=-2sin2x

    asked on July 24, 2011
  23. biology

    how is emigration and immigration not important factors when studying global human population growth?

    asked on May 25, 2010
  24. physics

    Assume that in interstellar space the distance between two electrons is about 0.68 cm. The electric force between the two electrons is 1. attractive. 2. repulsive. Calculate the electric force between these two electrons. The value of the Coulomb constant

    asked on April 9, 2020
  25. physics

    Two point charges are separated by 9 cm, with an attractive force between them of 18 N. Find the force between them when they are separated by 20 cm. The Coulomb constant is 8.99 × 109 N · m2 /C 2 . Answer in units of N.

    asked on April 9, 2020
  26. physics

    Calculate the electric force between these two electrons. The value of the Coulomb constant 9 × 109 N · m2/ C2 and the elemental charge is 1.6 × 10−19 C . Answer in units of N.

    asked on April 8, 2020
  27. physics

    A certain moving electron has a kinetic energy of 0.991 × 10−19 J. Calculate the speed necessary for the electron to have this energy. The mass of an electron is 9.109 × 10−31 kg. Answer in units of m/s. answer is ?

    asked on April 6, 2020
  28. math

    a plane flying at 33,000 feet is 13o miles away from the airport when it begins to descent.find the angleof depression of the plane to the starting point of the airport

    asked on February 8, 2020
  29. MATH


    asked on June 2, 2019
  30. English

    Compare and contrast the narrators in “And of Clay Are We Created” and “The Third Bank of the River.”

    asked on September 26, 2018
  31. Biology

    An example of homologous structures would be our front teeth and ___: a. the mandibles of a crab b. the mouthparts of a mosquito c. the beak of a bird d. the tentacles of a sea worm e. the front teeth of a horse I'm having difficult on which answer is

    asked on January 18, 2017
  32. Chemistry

    This same substance is a gas with a density of 1.25 g/L at 127o C and a pressure of 400 torr. What is its molar mass ?

    asked on December 11, 2016
  33. Math

    For f(x) = 3x + 4 and g(x) = x - 1. Calculate (f o g)(x). For f(x) = 3x + 2 and g(x) = x². Calculate (f o g)(-2). Consider the function. f(x)= -2x+1. Find the inverse of f(x). Please help! How do I solve this?

    asked on November 9, 2016
  34. Aviation Security

    Question 1 of 20 Why is microwave holographic imaging not being used as a security measure in U.S. airports? A. The cost is prohibitive. B. It violates the Fourth Amendment rights of passengers. C. It issues too many false alarms. D. Each passenger must

    asked on July 24, 2016


    asked on May 7, 2016
  36. AP Chemistry

    Determine the pH of an HF solution with a 4.70x10^-2M and 2.20x10^-2M. I tried this by looking up the Ka and putting it over molarity-ka squared. Am I doing something wrong? Can someone please show me the proper way to solve this problem?

    asked on February 9, 2016
  37. science

    what is the velocity of a 0.7 kg ball that has a momentum of 1.4 kg m/s

    asked on January 30, 2016
  38. Math

    David and Mike are brothers. David is 33 years old today. This is three times as old as Mike was when David was the age that Mike is today. How old is Mike?

    asked on October 14, 2015
  39. health

    How many American adults does OCD affect each year?

    asked on May 14, 2015
  40. physics

    An airplane of mass 1.30 104 kg is moving at 52.0 m/s. The pilot then increases the engine's thrust to 7.00 104 N. The resistive force exerted by air on the airplane has a magnitude of 3.00 104 N.

    asked on November 24, 2014
  41. physics

    a hemisphere container is made with the following dimensions. the external diameter of the container is 12 cm. the internal diameter of the container is 6 cm. it is filled with water to the brim. what is the density of the empty container if the total mass

    asked on September 2, 2014
  42. science

    a hemisphere container is made with the following dimensions. the external diameter of the container is 12 cm. the internal diameter of the container is 6 cm. it is filled with water to the brim. what is the density of the empty container if the total mass

    asked on September 2, 2014
  43. Science

    A car converts 1000 J of energy from a sample of fuel. 750 J of heat (thermal energy) is produced by the engine, 150 J of heat is produced in the transmission, drive train, etc., and 100 J of work is done to move the car. How efficient was the process of

    asked on August 8, 2014
  44. Math

    Helping grandson with math. I would like to know how to do it before he does. "How many different rectangles can be made with a perimeter of 20 units? (Remember, a square is also a rectangle.)"

    asked on May 25, 2014
  45. Physics

    A skater rotates 880 degrees clockwise, stops, and rotates counterclockwise for 340 degrees. What is her angular distance? Angular displacement?

    asked on August 6, 2013
  46. algebra

    steps to (.15x)+(-.3x)=

    asked on November 11, 2012
  47. Math

    A box with an open top is to be constructed from a rectangular piece of cardboard with dimensions 12 in by 12 in by cutting out equal squares of side x at each corner and then folding up the sides as in the figure. Express the volume V of the box as a

    asked on September 10, 2012
  48. Math

    A cylindrical can with both a top and bottom has the same surface area as a cube with edge 50mm. The height of the can if 6cm. Find the radius of the can to the nearest thousandth.

    asked on September 3, 2012
  49. Chemistry

    Rank the following from most polar to least polar (aspirin, caffeine, ibuprofen, acetaminophen): I am getting caffeine>acetaminophen>aspirin>ibuprofen. Is that correct?

    asked on September 2, 2012
  50. Math

    Use the Intermediate Value Theorem to show that there is a root of the given equation in the specified interval. x^4+x-3=0, interval (1,2). According the to theorem, I found that a is 1, b is 2 and N is 0. f(1)= 2 and f(2) = 17. Is the root (1.16,0)?

    asked on September 1, 2012
  51. Math

    Use a graph to find a number delta such that if abs(x-pi/4) < delta then abs(tanx-1) < 0.2. I understand that the epsilon is 0.2. But what step do I take next? How do I solve the problem?

    asked on September 1, 2012
  52. Math

    Prove that lim (x->0) x^4 cos 2/x = 0.

    asked on September 1, 2012
  53. Math

    Answer check please: Consider the circle (x-3)^2 + (y+1)^2 = 169. The point (15,4) is on the circle. Find an equation for the line that is tangent to the circle at this point. I got y= 5/12x-9/4.

    asked on August 26, 2012
  54. Math

    An oil tank is the shape of an inverted right circular cone with the pointed end down. The tank is 15 feet tall and is 12 feet in diameter at the top. At 1:00pm, the tank has oil 5 feet deep in it. Oil is pouring in at 5 cubic feet per minute. To the

    asked on August 26, 2012
  55. Math

    A truck tire with a diameter of 36 in is rolling over level ground spinning at 11 rotations/second. If the speed limit is 55 miles per hour and the penalty is $20 per hour over the speed limit, should the driver be fined and if so, how much?

    asked on August 26, 2012
  56. Math

    An isosceles triangle has its vertex at the origin and the ends of its base on the parabola y=9-x^2. Express the area of the triangle as a function of the length of its base. Assume its base lies above the x-axis.

    asked on August 26, 2012
  57. Chemistry

    How many milliliters of a .5M HNO3 (aq) is needed to completely neutralize 100mL of a 0.10M KOH (aq)?

    asked on May 30, 2012
  58. Biology

    Which of the following would be the most sigificant between mitosis and meiosis? A. Chromosomes are duplicated before mitosis B. Meiosis is not followed by cytokinesis C. Homologous Pairs of chromosomes are split up in meiosis. D. Crossing over occurs in

    asked on March 6, 2012
  59. Math

    There are 189 students in the band. The difference between the number of boys and the number of girls is 27. How many boys and girls each are in the band?

    asked on December 5, 2011
  60. Math

    Jun-Jee either ran 5 or 7 miles each day for 30 consecutive days. His total mileage during this period was 166> How many days did he run 5 miles? How many days did he run 7 miles?

    asked on December 5, 2011
  61. math

    If there are 264 students in a school and there are 84 eighth graders and There are 22 fewer seventh graders than sixth graders. Then which grade has the most students and how many students are there.

    asked on December 5, 2011
  62. trig

    5. If the angles X and Y each measure between 0° and 90°, and if sinX = cosY, what is the sum of the measures of the angles X and Y?

    asked on November 17, 2011
  63. geometry

    How would you write that line segment PK has equal length with line segment OQ?

    asked on November 14, 2011
  64. pre cal 2

    verify the identity tanx times cotx/cosx=secx

    asked on July 24, 2011
  65. Math

    What addition property can you use to find the missing number? 8+(6+5)=8+(5+_)

    asked on April 9, 2011
  66. us history

    I'm writing a paper about re-enlisting during the American Revolution, even though I'm miserable with the sick and dying all around me. I need to come up with a good grabber to start my paper with. Can you help?

    asked on March 16, 2011
  67. Economics

    How would a communist economy react to social and technological changes? What is the role of nature in a communist economy? I can't find any information on these subjects. Could someone please help me? Thanks so much

    asked on February 11, 2011
  68. math

    1.Robin has a certain number of dimes in his pocket. If the dimes were pennies, he would have $1.08 less than he has now. How many dimes does he have in his pocket?

    asked on January 27, 2011
  69. math

    1.Robin has a certain number of dimes in his pocket. If the dimes were pennies, he would have $1.08 less than he has now. How many dimes does he have in his pocket?

    asked on January 27, 2011
  70. Math percentages

    I have to compare two amounts given in percent. Last year, 80% of a cafe's sales were coffee; this year only 20% of the cafe's sales are coffee. How much has the percent of coffee sales changed over the past year. Is the answer simply down by 60% or is it

    asked on January 10, 2011
  71. Physics

    A 7.0 kg bowling ball moves at 2.40 m/s. How fast must a 2.60 g Ping-Pong ball move so that the two balls have the same kinetic energy?

    asked on December 10, 2010
  72. physics

    A 726 kg car travels from Boone to Blowing Rock along US321. How much working is needed to keep the car traveling at a constant speed of 21.8 m/s around a curve of radius 28.4 m?

    asked on December 5, 2010
  73. Physical Chemistry

    The equilibrium constant for a reaction was measured at several temperatures and the data plotted at right. The slope and y-intercept of the plot are +3.25 kK and -4.04, respectively. Calculate ΔrH(std), ΔrS(std), and ΔrG(std) using this information.

    asked on November 10, 2010
  74. Physical Chemistry

    A 100 amino acid folded protein (F) is in equilibrium with it’s unfolded (U) (or denatured) form. Let ΔrH(std) =+347 kJ mol-1 and ΔrS(std) =-1010 J K-1 mol-1 for the equilibrium (F U) at 25℃. (a) Calculate the concentration of protein in each form if

    asked on November 10, 2010
  75. Physical Chemistry

    Calculate the standard reaction Gibbs energy of the oxidation of ammonia to nitric oxide according to the equation 4 NH3g) + 5O2(g) → 4 No(g) + 6 H2O(g).

    asked on November 10, 2010
  76. math

    If the ratio of onions to cilantro is 4:3 and I'm using 2/3 cup of onions, how much cilantro will I need?

    asked on November 8, 2010
  77. Math

    Fireworks are fired at an angle of 82degrees with the horizontal. They are expected to explode about 100 m in the air, 4.8 secs after they are fired. What is the initial velocity of a shell fired from ground level. I think I have to find the vertical and

    asked on November 1, 2010
  78. Physics

    An artillery shell is fired with an initial velocity of 300 m/s at 65.0° above the horizontal. To clear an avalanche, it explodes on a mountainside 37.5 s after firing. What are the x and y components of the shell where it explodes, relative to its firing

    asked on October 20, 2010
  79. Physics

    A student stands at the edge of a cliff and throws a stone horizontally over the edge with a speed of 21.0 m/s. The cliff is h = 60.0 m above a flat horizontal beach. A)How long after being released does the stone strike the beach below the cliff? B)With

    asked on October 20, 2010
  80. science

    Provide specific examples from the Bridger Teton video as you defend your position.

    asked on June 17, 2010
  81. algebra

    list all the possible rational zeros of f using the rational zero theorem. then find all the zeros of the function. 1. f(x)=x^2-6x+5 2. f(x)=x^3+x^2-10x+8

    asked on May 23, 2010
  82. biology

    why is it important to understand challenges in a species' environment in order to understand the species' evolution? Relate your answer to what Darwin referred ti as "the struggle for survival".

    asked on May 22, 2010
  83. english

    In the book, When the Legends Die, what does it mean when Tom draws the deer in the dirt?

    asked on April 19, 2010
  84. social civics

    the three basic types of government: mayor-council plan, the commission, and the manger-council plan. give at least one strength and one weakness for them . and size of city where most effective thanks alot i cannot not seem to find this in my book

    asked on April 9, 2010
  85. college

    What are the three most important points you think a group of people must keep in mind when working collaboratively on a writing project? Why? Support your response with references to readings and personal experiences.

    asked on April 5, 2010
  86. Math

    I'm having trouble with reciprocal functions. If a graph of a reciprocal function is given, how do you find its equation? Any help would be really appreciated.

    asked on November 24, 2009
  87. Algebra

    I need this question put into an equation. I have been working on this forever and cannot figure out! Please explain what you did. Thanks so much for your time! Mark sold 105 tickets for the basketball game. Each adults ticket cost $2.50 and each child's

    asked on October 14, 2009
  88. Biology

    1. A famous scientist once said that wherever in the universe life exists, some of those life-forms must be colored. Why would the scientist make such a statement? 2. One of the accessory pigments used in photosynthesis is beta-carotene, a carotenoid found

    asked on October 12, 2009
  89. history

    can u please give me a site that will have a short but an informative article on the English Reformation? thnks

    asked on May 25, 2009
  90. Physics

    If a ball is sliding along a frictionless horizontal surface is the total work being done on the ball zero? I think so because there is no mention of applied force. Am I correct? P.S. On this holiday weekend, I want to send a BIG THANK YOU to all the

    asked on April 11, 2009
  91. Physics

    I don't know where to start with this one. "Find the work done accelerating a 2 kg box from 2m/s to 3 m/s." Can't find acceleration because I don't know time. In fact, I don't see how any of the kinematic equations can help me out to find either distance

    asked on April 6, 2009
  92. Physics

    I have a follow-up to my question at 4:10 about work because I still can't figure it out. F-F(friction)=ma F-F(friction)=2*3 F-2.5=2*3 F=2*3 + 2.5 W=Fd W=(2*3 + 2.5)4 Distributing the "4" I get W=2*3*4 +2.5*4 Please help in pointing out where I have gone

    asked on April 6, 2009
  93. Physics

    Calculate the work done by the applied force accelerating a 2 kg object at 3 m/s/s over 4 m if there is a 2.5 frictional force of resistance. I calculated using F=ma=6N; then net force = 6N-2.5N=3.5 N so W=fd=14J. Did I do this correctly? Thanks

    asked on April 6, 2009
  94. Physics

    I'm having a hard time with some free body diagrams. If you have a box on a slope/ramp and the angle of the ramp is X degrees why is it that the angle between the normal force and the gravitational force is also X degrees? Am I missing something obvious

    asked on March 26, 2009
  95. Physics

    I'm comparing the "g-force" of a rocket and a race car. My answer for the race car corresponds to the answer in the book but my answer for the rocket is off by 1. The book says I need to add 1 G because the rocket is going upward. So, instead of my answer

    asked on March 16, 2009
  96. com 220

    Why would it benefit you to try various sites rather than just get used to one? Why is it good advice to look for content as well as the date of the publication?

    asked on October 9, 2008
  97. sales tax

    swaetshirts are on sale for 26 dollars and are 15% off. what is the sales price before tax

    asked on April 26, 2008
  98. english

    Can soneone help me to combine each of the following groups of simple sentences into two longer sentences. Thanks 1. Darryl works as a model. He has to look his best. He gained ten pounds recently. He had to take off the extra weight. He would have lost

    asked on March 10, 2008
  99. Algebra 1b

    Factor completely 100r^2 + 160rt + 64t^2

    asked on March 8, 2008
  100. Algebra 1b

    Find all numbers for which the rational expression is undefined. p^3 - 4p/P^2 - 4

    asked on March 8, 2008


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