Popular questions and responses by Ana
  1. chemistry

    4g of a mixture of CaCO3 and sand is treated with an excess of HCl and 0.88g of CO2 is produced. What is the percentage of CaCO3 in the mixture

    asked on February 17, 2015
  2. Chemistry

    A solid white substance A is heated strongly in the absence of air. It decomposes to form a new white substance B and a gas C. The gas has exactly the same properties as the product obtained when carbon is burned in an excess of oxygen. Based on these

    asked on August 29, 2010
  3. Math

    The probability that a person stopping at petrol pump will get his tyres checked is 0.12, the probability that he will get his oil checked is 0.29 and the probability that he will get both checked is 0.07. A) what is the probability that a person stopping

    asked on December 9, 2016
  4. physics

    To stretch a certain spring by 2.00 cm from its equilibrium position requires 9.50 J of work. a. What is the force constant of this spring? b. What was the maximum force required to stretch it by that distance?

    asked on March 6, 2011
  5. (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

    asked on May 7, 2014
  6. 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

    asked on March 5, 2014
  7. Physics

    How many grams of water (H_2O) have the same number of oxygen atoms as 1.0 (mol} of oxygen gas? atomic mass of H is 1 and O is 16, so H2O has a molar mass of 18. Oxygen gas is O2, with a molar mass of 32. So 1.0 mole of oxygen gas has 6.02x10^23 molecules

    asked on November 18, 2009
  8. Calculus

    The shoreline of a lake is a circle with diameter 3 km. Peter stands at point E and wants to reach the diametrically opposite point W. He intends to jog along the north shore to a point P and then swim the straight line distance to W. If he swims at a rate

    asked on June 20, 2017
  9. Physics

    Four objects - a hoop, a solid cylinder, a solid sphere, and a thin, spherical shell - each has a mass of 4.59 kg and a radius of 0.252 m. (a) Find the moment of inertia for each object as it rotates about the axes shown in the table above. hoop____ kg·m2

    asked on March 19, 2010
  10. Math

    In a math class, each student who does not turn in a homework assignment receives a 0 for that assignment. Of the 10 students in the math class, what is the maximum possible number who did not turn in Homework assignment #1? We are given that one student's

    asked on July 16, 2020
  11. (2-8) Chemistry - Science (Dr. Bob222)

    Which of the following statements is correct? A) The internal energy of a system increases when more work is done by the system than the heat that flows into the system. B) The system does work on the surroundings when an ideal gas expands against a

    asked on May 11, 2014
  12. chem

    When the valve between the 2.00-L bulb, in which the gas pressure is 2.00 atm, and the 3.00-L bulb, in which the gas pressure is 4.50 atm, is opened, what will be the final pressure in the two bulbs? Assume the temperature remains constan

    asked on October 17, 2011


    asked on December 1, 2009
  14. Math

    A company is deciding between two different car models as it updates its fleet of cars. The purchase price for model A is $30,000, and the price for model B is $35,000. However, model A has an average gas mileage of 27 miles per gallon while model B’s is

    asked on August 11, 2020
  15. (12)Chemistry - Science (Dr. Bob222)

    Calculate delta E for a process in which 88.0 g of nitrous oxide gas (N2O) is cooled from 165 ˚C to 65 ˚C at a constant pressure of 5.00 atm. The molecular weight of nitrous oxide is 44.02 g/mol, and its heat capacity at constant pressure, Cp, is 38.70

    asked on May 8, 2014
  16. Physics

    What is the gas pressure inside the box shown in the figure? I have a picture but website wouldn't allow me to post the link for the picture. So I am trying my best to describe it. it is a u-shape tube and it is holding mercury in it. One side has 16cm of

    asked on November 15, 2009
  17. physics

    In a friendly game of handball, you hit the ball essentially at ground level and send it toward the wall with a speed of 17 m/s at an angle of 39 ∘ above the horizontal. How long does it take for the ball to reach the wall if it is 3.8 m away? How high

    asked on February 20, 2017
  18. 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

    asked on April 15, 2014
  19. chemistry

    how could one distinguish 1-octanol from 1-octene and toluene from 1- octene?

    asked on October 8, 2009
  20. Physics/ can Dr. help me

    How many grams of water (H_2O) have the same number of oxygen atoms as 1.0 (mol} of oxygen gas?

    asked on November 18, 2009
  21. Art

    Bourgeois by Alfred Jacob Miller Look at the following illustration of an early american settler. it would likely inspire a writer to create a story based on all of the following historic information except A) the clothing worn by the individuals B) the

    asked on September 30, 2015
  22. Math

    Jaden wants to cover the floor with square tiles the same size. The floo measures 315 inches by 108 inches. If she uses only whole tiles, find A) the greatest possible length of each tile B) the number of tiles needed to cover the floor.

    asked on December 26, 2012
  23. Physics

    A synchronous satellite, which always remains above the same point on a planet's equator, is put in orbit around Neptune so that scientists can study a surface feature. Neptune rotates once every 16.1 h. Use the data of Table 13.2 to find the altitude of

    asked on March 13, 2010
  24. Science

    Scoop ice cream into 8 - 1/2 cup sized balls. Place on baking sheet and freeze until firm, about 1 hour. 3 egg whites 1)What is the radius of each ball? You can either approximate based on the volume measurement of each ice cream ball in the recipe 118

    asked on June 16, 2020
  25. geometry

    Which of these is a correct step in constructing congruent line segments? a) use a straightedge to draw two equal arcs from the endpoints. b) use a compass to join the endpoints of the line segment. c) use a straightedge to measure the length of the line

    asked on October 5, 2015
  26. MATH

    the line 'l' has gradient 3 and cuts the x-axis at 4 then its equation?

    asked on December 10, 2016
  27. chemistry

    Determine the electron geometry, molecular geometry, and idealized bond angles for each of the following molecules. In which cases do you expect deviations from the idealized bond angle?1.pf3 2.sbr2 3.ch3br 4.bcl3

    asked on August 23, 2012
  28. Chemistry

    Can zinc (Zn) react with one of these: Al(NO3)3 aluminum nitrate Mg(NO3)2 magnesium nitrate Zn(NO3)2 zinc nitrate Cu(NO3)2 copper nitrate?

    asked on March 7, 2010
  29. Science

    Calculating diffusion coefficient You want to make meatballs according to a recipe that says to marinate the meatballs in garlic and soy sauce before baking them in the oven. You prepare the marinade and immerse the meatballs, which are 6 cm in diameter,

    asked on June 16, 2020
  30. Physics

    Can you help me please? A slice of pizza contains about 290 Calories, which is equal to about 1200 Kilojoules. If you burned your pizza as fuel to power an oven with a 1000W output, how long would one slice power this oven? Assume complete conversion of

    asked on May 12, 2020
  31. physics

    Two springs, with force constants k1=175N/m and k2=270N/m, are connected in series When a mass m=0.50kg is attached to the springs, what is the amount of stretch, x?

    asked on March 27, 2017
  32. Math

    Student A, B and C con complete a puzzle in 20 min, 15 min, and 30 min respectively. If all three student work together, how long will it take to complete the puzzle?

    asked on November 16, 2015
  33. 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

    asked on May 7, 2014
  34. Physics

    The 3.0 cm-diameter water line splits into two 1.0cm-diameter pipes. All pipes are circular and at the same elevation. At point A, the water speed is 2.0m/s and the gauge pressure is 50kPa. What is the gauge pressure at point B?(pointing toward one of the

    asked on November 17, 2009
  35. Physics

    Which two factors are in balance when a material transitions between two phases? a)Interaction Energy b)Thermal Energy c)Boiling temperature d)Freezing temperature e)Boltzmann Constant my answer A & D

    asked on May 26, 2020
  36. Math

    Nine boxes contain cans of different weights. How could you redivide the cans so each box weighs the same? There is 1 box with cans and the box weights ⅓, 1 box weights ⅔, 2 boxes weights 1⅓, 2 boxes weights 2⅔, and 3 boxes weights 3 pounds.

    asked on April 1, 2018
  37. math

    the 54th term and 4th term of an A.P are -61 and 64 respectively.Find the common difference and 23rd tem

    asked on November 30, 2016
  38. math

    5 oranges when removed from a basket containing three more than seven times as many oranges,leave how many oranges in the basket?

    asked on November 14, 2016
  39. Math

    How many times greater is the value of the 2 in the thousands place than the 2 in the tens place in the number 742,025?

    asked on August 29, 2016
  40. math

    alyssa has saved 26 quarters from washing cars. how many cents does alyssa have?

    asked on October 14, 2014
  41. Chemistry

    Aluminum sulfate reacts with calcium hydroxide (from lime) to form aluminum hydroxide and calcium sulfate. Write the balanced formula unit equation for the reaction.

    asked on September 28, 2014
  42. 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

    asked on January 21, 2013
  43. physics

    Two carts, one twice as heavy as the other, are at rest on a horizontal frictionless track. A person pushes each cart with the same force for 6.00 s. If the kinetic energy of the lighter cart after the push is K, the kinetic energy of the heavier cart is

    asked on March 6, 2011
  44. chemistry

    Tetraphosphorus trisulphide (P4S3) is used in the match heads of some matches. It is produced in the reaction 8P4+3S8 --> 8P4S3. Determine which of the following statements are incorrect, and rewrite the incorrect statements to make them correct. a. 4 mol

    asked on April 6, 2010
  45. Chemistry

    Calculate the enthalpy change for the following equation: NO(g)+ 1/2O2(g) -----> NO2(g) I have no clue how to do this. I just know the answer is supposed to be approximately -57.2 kJ. Can some explain to me what to do?

    asked on March 28, 2010
  46. Physics

    A 1.80-cm-thick wood floor covers a 4.0 m times 5.5 m room. The subfloor on which the flooring sits is at a temperature of 16.1C, while the air in the room is at 19.2 C. What is the rate of heat conduction through the floor? Use 0.200 W/m* K for the

    asked on December 3, 2009
  47. Chemistry

    Mrs. Wilson leaves her freshly-baked blueberry pie on the windowsill to cool. The delicious fragrance diffuses through the air with a diffusion coefficient of D = 0.2 cm2/s. How long does it take for Dennis to smell the pie in his treehouse 10 meters away?

    asked on June 18, 2020
  48. College Algebra

    How much water must be evaporated from 32 ounces of a 7% salt solution to make a 8% salt​ solution? (Answer is in ounces)

    asked on August 27, 2017
  49. Health

    An individuals self-esteem stays the same throughout their life: A - true B - false ** Self-actualization means that you focus on yourself all the time A - true B - false ** Which of the following is a skill you can practice to improve your self-esteem? A

    asked on October 3, 2016
  50. calculus

    A water tank has the shape of an inverted right circular cone with base radius 3 meters and height 6 meters. Water is being pumped into the tank at the rate of 12 meters3/sec. Find the rate, in meters/sec, at which the water level is rising when the water

    asked on April 25, 2015
  51. Algebra

    Gerry had a total of 30 pens and pencils. He decided to trade with his friends all of his pens and pencils. If he traded every pen for 2 pencils, he would have 48 pencils in all. How many pens and how many pencils did he have before the trade?

    asked on November 19, 2014
  52. statistics

    find the probability p(-1.14 < z < 1.01) using the normal standard distribution

    asked on April 18, 2012
  53. chemistry

    How many iron atoms are in 0.32 mol of Fe2O3

    asked on February 20, 2012
  54. Statistics

    Do more than 50% of US adults get enough sleep? According to the Gallup organization's December 2004 Lifestyle Poll, 55% of US adults said that they get enough sleep. The poll was based on a random sample of 1003 adults. Test an appropriate hypothesis and

    asked on May 15, 2011
  55. trig/math

    Two ships leave a harbor together traveling on courses that have an angle of 124° between them. If they each travel 511 miles, how far apart are they (to the nearest mile)?

    asked on March 31, 2010
  56. Physics

    A 0.006-kg bullet traveling horizontally with a speed of 1.00 103 m/s enters an 21.1-kg door, imbedding itself 10.4 cm from the side opposite the hinges as in the figure below. The 1.00-m-wide door is free to swing on its hinges. (c) At what angular speed

    asked on March 19, 2010
  57. Chemistry

    2KClO3 --> 2KCl + 3O2 What mass of O2 can be made from heating 125 g of KClO3? I know that the answer is 49 g O2 but I keep getting a completely different answer, can anyone show me what I'm doing wrong? 125g KClO3 x (2 mol KClO3/ 122.49g KClO3) = 2.04 mol

    asked on March 2, 2010
  58. Math

    Anton is four years older than Liza. The product of his age three years from now and Liza's age two years ago is 90 years.Find their present ages

    asked on July 12, 2018
  59. Chemistry

    How could I tell if an element is stable or unstable? One of the examples is 89/42 Mo The only rule I know entirely is that if the atomic number is greater then 83 then it is unstable. Thanks

    asked on January 25, 2016
  60. chemsitry

    A graduated tube, sealed at the upper end has a mercury leveling bulb connected to the lower end. the gas volume is, when the mercury level is the same in both ends. the barometric pressure is 732 mm Hg. What is the gas volume when the mercury level

    asked on December 2, 2015
  61. us history

    which of the following describes the first British colony at Jamestown? a) it did not have the right sol and climate for tobacco crops. b) the settlers there had a lack of fresh water. c) the colony would not have thrived without the Powhatan tribe.******

    asked on October 30, 2015
  62. us history

    which of the following illustrates the concept of civic virtue? a) helping the economy grow b) doing things for the common good ** c) making the government strong d) becoming wealthy individual please help thanks means alot

    asked on October 26, 2015
  63. english

    In "The Maori: Genealogies and Origins in New Zealand,” which evidence best helps the reader infer that the Maori people live in a difficult climate?

    asked on September 16, 2015
  64. math

    The side length of a rectangular box with a square base is increasing at the rate of 2 ft/sec, while the height is decreasing at the rate of 2 ft/sec. At what rate is the volume of the box changing when the side length is 10 ft and the height is 12 ft?

    asked on April 26, 2015
  65. Chemistry

    1.2048g sample of impure Na2CO3 is dissolved and allowed to react with a solution of CaCl2 resulting CaCO3 after precipitation, filtaration and drying was found to weight 1.0362g. calculate the percentage purity of Na2CO3

    asked on February 14, 2015
  66. (1-13) Chemistry - Science

    Which of the following effects will make the ratio (PV) / (nRT) less than 1 for a real gas? a) The gas molecules are large enough to occupy a substantial amount of space. b) A large number of molecules have speeds greater than the average speed. c) The gas

    asked on May 10, 2014
  67. Physical Science

    A bicycle pump contains 250cm3 of air at a pressure of 90kPa, the volume is reduced to 200cm3. What is the pressure of the air inside the pump? a. 75 kPa b. 220 kPa c. 112.5 kPa d. 240.4 kPa

    asked on July 1, 2020
  68. Chemistry

    Heat Transfer heat diffused in our tuna steak was about 12 mm in 5 minutes. Using these values for L and for t, calculate the value of D for this time point. Enter your answer in cm2/sec, without including the units.

    asked on June 8, 2020
  69. stats

    Jason, a freshman at a local college, just completed 15 credit hours. His grade report is presented below. Course: Calculus, Biology, English, Music, P.E. Credit Hours 5, 4, 3, 2, 1 Grades C, A, D, B, A The local university uses a 4 point grading system,

    asked on September 15, 2016
  70. Physics

    A 200 N box is pushed up an incline 10 m long and 3 m high. The average force (parallel to the plane) is 120 N. a.) How much work is done? b.) What is the change in the PE of the box? c.) What is the change in KE of the box? d.) What is the frictional

    asked on October 27, 2015
  71. science

    Which of the following is an example of inbreeding? A) a farmer chooses the cos in his or her herd that produce he most milk and breeds only those cows. b) a farmer chooses the cows in his or herd that produces the most milk and breeds them with cows that

    asked on October 19, 2015
  72. language arts

    in ¨Harriet Tubman¨ what main idea do the details about William still´s records support? A) the fugitives´ trip north was difficult. b) the escaping slaves were not able to carry much with them as they traveled north. c) Harriet Tubman was justified i

    asked on October 14, 2015
  73. Chemistry

    A 5.00 g mixture of methane (CH4) and ethane (C2H6) is combusted in oxygen gas to produce carbon dioxide and water. If 14.09 g of CO2 is produced, how many grams of methane was in the original 5.00 g mixture ?

    asked on January 21, 2015
  74. Math

    Find the first 3 common multiples for 6,7,8.

    asked on October 19, 2014
  75. Chemistry - Science (Dr. Bob222)

    Hydrazine is used as a rocket fuel because its reaction with oxygen is extremely exothermic: N2H4(liquid) + O2(g)  N2(g) + 2H2O(liquid) ΔH(reaction) = -615 kJ mol-1 What is the enthalpy of this reaction if water were produced in the gaseous rather than

    asked on May 8, 2014
  76. 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

    asked on May 3, 2014
  77. 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

    asked on May 3, 2014
  78. physics

    B. Assume the child is 1.2 meters tall and casts a shadow of 6.4 meters. Determine the angle of the sun at that moment.

    asked on September 6, 2012
  79. algebra

    How can you divide 64 into 2 groups ti get a ratio of 3 to 5?

    asked on October 3, 2011
  80. chemistry

    when ammonia is added to Zn(NO3)2 solution, a white precipitate forms, which dissolves on the addition of excess ammonia. But when ammonia is added to a mixture of Zn(NO3)2 and NH4NO3, no precipitate forms at any time. Suggest an explanation for this

    asked on April 2, 2011
  81. Math Algebra 2

    A rectangular garden is fenced on three sides with a wall forming the fourth side. the total length of the fence is 70m. the area if the garden is 600m^2. find the dimensions of the garden.

    asked on March 20, 2011
  82. algerba

    which is the simplest form of the radical expression sqrt (10)+6sqrt(10)+-3sqrt(10)

    asked on July 12, 2010
  83. Life science

    Grade 11 learners want to investigate which enzyme is responsible for chemical digestion of starch into glucose in humans.They are provided with two different enzymes ( carbohydrase and protease),starch powder,warm water at about 37 degrees Celsius and

    asked on June 9, 2019
  84. math

    an arithmetic series is such that the ninth term is zero and the sum of first 25 terms is 50.the first term of the series?

    asked on December 7, 2016
  85. I need help - precalc

    List all points on the graph of y=tanx on the interval [π/2,3π] that have a​ y-coordinate of -1/radical3 (Direction- Type ordered pair)

    asked on August 4, 2016
  86. math

    marsha is 10 years older than john, who is 16 years old ? how old is marsha?

    asked on November 23, 2015
  87. us history

    Use the passage to answer the following question: I can see no reason to doubt but the imposition of taxes, whether on trade, or on land, or houses, or ships, on real or personal, fixed or floating property, in the colonies is absolutely irreconcilable

    asked on October 30, 2015
  88. us history

    which of the following represents the civic virtue of diversity? a) being open to the opinions of others b) seeking honesty in oneself c) arguing a point based on facts d) focusing on individual rights** please help thanks very much

    asked on October 26, 2015
  89. Math Decimals

    Jason has 4 tiles. Each tile has a number printed on it. The numbers are 2,3,6, and 8. A decimal number is formed using the tiles and the clues. Be a math detective and find the number. Clues: digit in tens place is the greatest number. digit in tenths is

    asked on October 12, 2015
  90. physics

    the magnetic force on a straight 0.15m segment of wire carrying a current of 4.5 A is 1.0 N. What is the magnitude of the component of the magnetic field that is perpendicular to the wire?

    asked on May 17, 2012
  91. chemistry

    which of the following molecules can have optical isomers? a. CH2Cl2 b. H2NCH(CH3)COOH c. ClCH(OH)CH2Cl is b and c

    asked on June 25, 2010
  92. chemistry

    Ammonia and oxygen react to form nitrogen and water. 4NH3(g)+3 O2(g)-2N2(g)+6H2O(g) a.How many grams of O2 are needed to react with 8.00 mol NH3? 8.00 mol NH3 x42.094/4 mol NH3 x32.00 O2/1 mol O2=269gO2

    asked on June 25, 2010
  93. Chemistry

    I have these two questions on my section review that I don't know how to answer. Can someone help me? Please and thank you. 3. Describe in your own words how to prepare 100 mL of a .85 M solution of sodium chloride. 4. If you dissolve 2.00 mol KI in 1.00 L

    asked on April 29, 2010
  94. Chemistry

    Classify the following mixtures as homogenous(H) or heterogenous(HT): a.lemon juice-H (I'm guessing there's no pulp) b.tap water - H c.blood- HT paint- H I'm not sure about a and D

    asked on April 27, 2010
  95. Phy

    98N-T=10a T-18.89N=3a I worked on the problem and I end up getting two equations but now I have to find T and a. For some reason, I cant solve it. Thanks

    asked on February 28, 2010
  96. Physics

    0.75 mol of argon gas is admitted to an evacuated 40 cm^{3} container at 40 C. The gas then undergoes an isochoric heating to a temperature of 500 C. What is the final pressure of the gas?(answer in kPa)

    asked on December 10, 2009
  97. Physics

    This is the last time I'm posting this question. So pleas don't get mad. How many atoms of hydrogen are in 220 g of hydrogen peroxide (H2O2)? (220)/(34) then i multiply that # with 6.02E23 then again i multiply that # with 2 to get the number of hydrogen

    asked on November 22, 2009
  98. Physics

    On a cool morning, when the temperature is 13 C, you measure the pressure in your car tires to be 30 psi. After driving 50 mi on the freeway, the temperature of your tires is 42C. What pressure will your tire gauge now show? T1 = 13 C T2 = 42 C P1 = 30 psi

    asked on November 19, 2009
  99. Physical Science

    A bicycle pump contains 250 cm3 of air at a pressure of 90 KPa. If the air is compressed, the volume is reduced to 200 cm3. What is the pressure of the air inside the pump? use p1v1 = p2v2 V1 = 90 and V2 = P1= 250 cm and p9= 200 P1V1 = p2V2 V2=p1V1/p2

    asked on July 1, 2020
  100. Chemistry

    I’ve tried everything but just can’t get it. Write the reaction between solutions of mercury (II) nitrate and sodium sulfide. a) how many moles of sodium nitrate form from the reaction of 2.85 mol of sodium sulfide? b) how many litres of 0.150 mol/L

    asked on June 8, 2020


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