# Rachel

Most popular questions and responses by Rachel
1. ## Chemistry

3NO2(g) + H2O(l) → 2HNO3(aq) + NO(g) standard enthalpy: -133.5 Find the change in internal energy for this reaction. Enter in kJ.

2. ## Physics

A child's game consists of a block that attaches to a table with a suction cup, a spring connected to that block, a ball, and a launching ramp. By compressing the spring, the child can launch the ball up the ramp. The spring has a spring constant k, the

3. ## Pre calc

sin(θ − ϕ); tan(θ) = 5/12 θ in Quadrant III, sin(ϕ) = − sqaure root 10/10 ϕ in Quadrant IV I tried this numerous times can somone please help me

4. ## Chemistry 120

* If 13.3 kilograms of Al2O3(s), 58.4 kilograms of NaOH(l), and 58.4 kilograms of HF(g) react completely, how many kilograms of cryolite will be produced? * Which reactants will be in excess? *What is the total mass of the excess reactants left over after

5. ## Algebra

A kite is tied to the ground. The rays from the sun hit the kite perpendicular to the kite string, casting a shadow of the kite on the ground. The coordinates in the diagram are given in feet. What is the distance from where the kite is tied to the shadow?

6. ## History

1.As a result of the French and Indian War, ___ claimed all land west of the Mississippi River, and ___ gained control of all land east of it. a. Indians; Britain b. Spain; France c. France; Indians d. Spain; Britain If you have any other answers to this

7. ## Physical Science

A 0.6-g peanut is burned beneath 50 g of water, which increases in temperature from 22degreesC to 50 degreesc. What is the exact food value of the peanut? (Assuming a 40% efficiency)

8. ## Physics

A certain spring stretches 5.8cm when a load of 38N is suspended from it. How much will the spring stretch if 48N is suspended from it (and it doesn't reach its elastic limit)?

9. ## Statistics

A coffee company wants to make sure that there coffee is being served at the right temperature. If it is too hot, the customers could burn themselves. If it is too cold, the customers will be unsatisfied. The company has determined that they want the

10. ## physics

A man lifts various loads with the same lever. The distance of the applied force from the fulcrum is 2.00 m and the distance from the fulcrum to the load is 0.500 m. A graph of resistance force vs. effort force is shown. What is the mechanical advantage of

11. ## physics conservation of momentum

A 0.5 kg ball is thrown horizontally towards a wall with a speed of 10 m/s. The initial velocity is chosen to be the positive x-direction for this question. The ball horizontally rebounds back from the wall with a speed of 10 m/s in the negative

12. ## chemistry

Determine the theoretical yield of C when each of the following amounts of A and B are allowed to react in the generic reaction: A+2B-->3C 1) 1mol A; 1 mole B 2) 1mole A; 3 mole B 3) 2mole A; 2 mole B 4) 32mole A; 68 mole B

13. ## Gen Chem 1

A tanker truck carrying 2.01×10^3kg of concentrated sulfuric acid solution tips over and spills its load. The sulfuic acid is 95.0% H2SO4 by mass and has a density of 1.84g/L. Sodium Carbonate (Na2CO3)is used to neutralize the the sulfuric acid spill. How

14. ## Algebra 1

A pyrotechnician plans for two fireworks to explode together at the same height in the air. They travel at speeds shown at the right. Firework B is launched 0.25 s before Firework A. How many seconds after Firework B launches will both fireworks explode?

15. ## chemistry

how many atoms of each element are present in five formula units of calcium permanganate?

16. ## physics

Two very long, straight, parallel wires carry currents that are directed perpendicular. Wire 1 carries a current I1 into the page (in the -z direction) and passes through the x axis at x = +a. Wire 2 passes through the x axis at x = -2a and carries an

17. ## physics

An accelerating voltage of 2.46 * 10^3 V is applied to an electron gun, producing a beam of electrons originally traveling horizontally north in vacuum toward the center of a viewing screen 34.0 cm away. What is the magnitude of the deflection on the

18. ## Science

The water molecules now in your body were once part of a molecular cloud. Only about onemillionth of the mass of a molecular cloud is in the form of water molecules, and the mass density of such a cloud is roughly 4.0×10−21 {\rm g}/{\rm cm}^{3} Estimate

19. ## Physics

The magnitudes of the four displacement vectors shown in the drawing are A = 14.0 m, B = 11.0 m, C = 12.0 m, and D = 25.0 m. Determine the (a) magnitude and (b) direction for the resultant that occurs when these vectors are added together. Specify the

20. ## Chemistry

what is the name for the following coordination compounds or ions? 1. [Al(H2O)6] Br3 2. [Cr(NH3)6] Cl3 3. K3[FeF6] 4. [Zn(OH)4]-2

21. ## AP Calc. AB

At how many points on the curve y=4x^5-3x^4+15x^2+6 will the line tangent to the curve pass through the origin?

22. ## phyics

A dart leaves the barrel of a blowgun at a speed v. The length of the blowgun barrel is L. Assume that the acceleration of the dart in the barrel is uniform. Find a time that the dart moves inside the barrel. Express your answer in terms of the variables L

23. ## Chemistry

A base has a Kb of 2.5 x 10–11. Which of the following statements is true? This is a concentrated base. This base ionizes slightly in aqueous solution. This is a strong base. An aqueous solution of this base would be acidic.

24. ## Chemistry

Hi, I posted yesterday with this lab question. "Calculate the molar amounts of NaOH used in the reaction with the HCl solution and with the HC2H3O2. I think I got the answer to that with the help that I received. I had 5 mL of HCl, and I was using .100 M

25. ## chemistry

the value for the Ksp of silver chromate is reported to be 1.1 x 10^-12. in a saturated solution of silver chromate, the silver ion concentration is found to be 2.5 x 10^-4M. what must the chromate ion concentration be?

26. ## life orienttion

Identify six symptoms of interpersonal conflict in a person

27. ## AP CALC. AB

A particle moves along a line so that at time t, where 0

A toy rocket is launched form a 3m platform, at 8.2m/s. The height of the rocket is modelled by the equation h=-4.0t^2+8.1t+3 where h is the height, in metres, above the ground and t is the time, in seconds. After how many seconds will the rocket rise to a

29. ## Algebra 1 HELP PLEASE!

suppose P equals {0,1,2,3,4,5,6,7,8,9} and V equals {2,4,6,8,10,12,14,16,18,20}. What is P (circle) V?

30. ## science

Four racecars are driving at constant speeds around a circular racetrack. The data table gives the speed of each car and each car’s distance from the center of the track at one instant. Car Speed (m/s) Position (m) A 40 20 B 40 25 C 50 20 D 50 25 Rank

31. ## Chemistry

Phosphoric acid, H3PO4(aq), is a triprotic acid, meaning that one molecule of the acid has three acidic protons. Estimate the pH, and the concentrations of all species in a 0.200 M phosphoric acid solution. pKa1 = 2.16 pKa2 = 7.21 pKa3 = 12.32 Ok I haven't

32. ## Physics

Julie throws a ball to her friend Sarah. The ball leaves Julie's hand a distance 1.5 meters above the ground with an initial speed of 24 m/s at an angle 32 degrees; with respect to the horizontal. Sarah catches the ball 1.5 meters above the ground. What is

33. ## Chemistry

Calculate the pH of a buffered solution that is 0.100M in C6H5COOH (benzoic acid, Ka = 6.4 x 10-5) and 0.100M in sodium benzoate (NaC6H5COO).

34. ## Forensics

Strontium-90 is a radioactive waste product from nuclear reactors. It has a half life of 29 years. How many years would it take for a quantity of strontium-90 to decay 1/16 of its original mass?

35. ## pre calc

To measure the height of the cloud cover at an airport, a worker shines a spotlight upward at an angle 75° from the horizontal. An observer D = 600 m away measures the angle of elevation to the spot of light to be 45°. Find the height h of the cloud

36. ## chemistry

Aqueous silver nitrate reacts with aqeous potassium iodide in a double-replacement reaction to produce a precipitate of silver iodide. If 34.6 ml of 0.563 M silver nitrate are used with 148.4 ml of potassium iodide: a) What molarity of potassium iodide

37. ## calculus

the cross section of a 5-ft long trough is an isosceles trapezoid with a 2 foot lower base, a 3-foot upper base, and an altitude of 2 feet. water is running into the trough at a rate of 1 cubic foot per minute. how fast is the water level rising when the

38. ## Chemistry

What is the hybridization of phosphorous in a P4 molecule

39. ## chem

A flexible container at an initial volume of 4.11 L contains 7.51 mol of gas. More gas is then added to the container until it reaches a final volume of 15.9 L. Assuming the pressure and temperature of the gas remain constant, calculate the number of moles

40. ## Chem (repost)

Hydrogen and carbon dioxide react at a high temperature to give water and carbon monoxide. H2(g) + CO2(g) --> H2O(g) + CO(g) (b) Suppose 0.052 mol each of H2 and CO2 are placed in a 1.5 L container. When equilibrium is achieved at 986°C, what amounts of

41. ## calculus

The side of a square is measured to be 12 inches with a possible error of ±0.02 inch in that measurement. If x is the exact length of the side of the square, express this difference as an absolute value inequality and solve. Then find the interval

42. ## physics

A 625-kg racing car completes one lap in 14.3 s around a circular track with a radius of 55.0 m. The car moves at constant speed. (a) What is the acceleration of the car?

52. ## Calculus

Let g and h be any two twice-differentiable functions that are defined for all real numbers and that satisfy the following properties for all x: I) (g(x))^2 + (h(x))^2=1 ii) g'(x)= (h(x))^2 iii) h(x)>0 iv) g(0)=0 a)Justify that h'(x)=-g(x)h(x) for all x b)

53. ## Physics

A small ball rolls horizontally off the edge of a tabletop of height h. It strikes the floor a distance x horizontally away from the edge of the table. (Use any variable or symbol stated above along with the following as necessary: g.) (a) How long is the

54. ## chemistry

write a net ionic equation for the following: 1)Iron (III) chloride reacts with Potassium hydroxide to produce Iron (III) oxide, Potassium chloride, and Hydrogen gas. 2)Hydrochloric acid reacts with Potassium carbonate to produce Potassium chloride,

55. ## math

David and Peter had $90 and$200 respectively. They were each given an equal amount of money. Then Peter had twice as much money as David. How much money did each boy receive?

56. ## Calculus- Can you help me solve for dr/dt

How fast does the radius of a spherical soap bubble change when you blow air into it at the rate of 15 cubic centimeters per second? Our known rate is dv/dt , the change in volume with respect to time, which is 15 cubic centimeters per second. The rate we

57. ## Chem

A sealed container holding 0.0255 L of an ideal gas at 0.989 atm and 71 °C is placed into a refrigerator and cooled to 45 °C with no change in volume. Calculate the final pressure of the gas.

58. ## Math

3 similar shirts and 4 similar jackets cost $360. 1 such shirt and 3 such jackets cost$220. Find the cost of each shirt.

59. ## physic

Suppose a runner completes one lap around a 400-m track in a time of 50 s. Calculate the average speed of the runner. please explain process

60. ## calculus

a billboard 20ft tall is located on top of a building with its lower edge 60 ft above the level of a viewers eye. how far from a point directly below the sign should a viewer stand to maximize the angle (theta) between the lines of sight of the top and

61. ## Chem

A balloon is inflated to a volume of 7.0 L on a day when the atmospheric pressure is 765 mmHg. The next day, as a storm front arrives, the atmospheric pressure drops to 725 mmHg. Assuming the temperature remains constant, what is the new volume of the

62. ## Genetics

Question 11 (1 point) Save As the degree of relatedness within a population increases, the level of inbreeding in that population also increases. As relatedness and inbreeding go up, individuals become more similar genetically and therefore genetic

63. ## Physics

Suppose that in the same Atwood setup another string is attached to the bottom of m1 and a constant force f is applied, retarding the upward motion of m1. If m1 = 5.30 kg and m2 = 10.60 kg, what value of f will reduce the acceleration of the system by 50%?

64. ## Physics

A 45 kg trunk is pushed 7.8 m at constant speed up a 30° incline by a constant horizontal force. The coefficient of kinetic friction between the trunk and the incline is 0.23. a)Calculate the work done by the applied horizontal force. b)Calculate the work

65. ## Algebra

Geppetto is a puppet maker. He starts the month with 3 puppets ready to sell, and makes 9 puppets per day. Write an equation to model this situation (use d for days and p for puppets).

66. ## calculus

water is poured into a conical paper cup so that the height increases at the constant rate of 1 inch per second. if the cup is 6 inches tall and its top has a radius of 2 inches, how fast is the volume of water in the cup increasing when the height is 3

67. ## chemistry

What is Delta H rxn for the following chemical reaction? H2O(l) + CCl4(l)-> COCl2(g) + 2HCl(g)

68. ## chem

A hot air balloon is filled with 1.51 × 106 L of an ideal gas on a cool morning (11 °C). The air is heated to 103 °C. What is the volume of the air in the balloon after it is heated? Assume that none of the gas escapes from the balloon.

69. ## AP Chemistry

(DrBob222 please help me) A sample of 1.97 grams of Z is dissolved into 500 grams of water which is in a styrofoam coffee cup. The temperature is monitored and is found to rise from 25.015◦C to 25.484◦C. What is ∆Hsolution for substance Z? Assume no

70. ## AP CALC

At any time t=>0 , in days, the rate of growth of a bacteria population is given by y' = ky, where y is the number of bacteria present and k is a constant. The initial population is 1500 and the population quadrupled during the first two days. By what

71. ## physics

An accelerating voltage of 2.46 * 10^3 V is applied to an electron gun, producing a beam of electrons originally traveling horizontally north in vacuum toward the center of a viewing screen 34.0 cm away. What is the magnitude of the deflection on the

72. ## Chemistry

Can someone please check my work? Calculate the mass of (NH4)2S2O8 needed to prepare 250mL of a 0.100M solution. I got 5.705 g. Calculate the volume of 2.00M KI needed to prepare 250mL of a 0.200M solution. I got 0.025L or 25mL. Calculate the volume of

73. ## chemistry

For each of the following acid-base reactions, calculate how many grams of each acid are necessary to completely react with and neutralize 2.1g of the base. 1) HCl(aq)+NaOH(aq)-->H2O(l)+NaCl(aq) 2) 2HNO3(aq)+Ca(OH)2(aq)-->2H20(l)+Ca(NO3)2(aq) 3)

The combusion of glucose produces carbon dioxide and water vapor according to the chemical equation below: C6H12O6 (s) + 6O2 (g) ---> 6CO2 (g) + 6H2O (g) DELTA H = -2540 kj Calculate the energ involved in making 75.0 g of glucose from carbon dioxide and

75. ## Statisics

The closing price of Schnur Sporting Goods Inc. common stock is uniformly distributed between $23 and$37 per share. What is the probability that the stock price will be: More than $33? Less than or equal to$27?

I have a question about the short story "Son" by John Updike. I have research this and read it but find it very confusing-I have two answers totally eliminated and would just like some input-Thank you so much Is "Son told in a.order from the contemporary

77. ## AP Chemistry

The reaction of 5.7 grams of fluorine with excess chlorine produced 7.6 grams of ClF3. What percent yield of ClF3 was obtained? Answer in units of %.

78. ## calculus 2

A tomato is thrown upward from a bridge 23 m above the ground at 40 m/sec. Take the acceleration of gravity be equal to 9.8 m/s^2 (a) Give formulas for the acceleration, velocity, and height of the tomato at time t. (b) How high does the tomato go, and

79. ## chemistry

How many liters of a 0.530M sucrose (C12H22O11) solution contain 1.3kg of sucrose?

80. ## AP Calc. AB

1.If an arrow is shot upward on the moon with a velocity of 50 m/s its height (in meters) after t seconds is given by H = 50t - 0.66t2. With what velocity will the arrow hit the moon? a. -49.5 b. -47 c. -50.1 d. -50 e. -51 2.If an arrow is shot upward on

81. ## chemistry

The directions state "weigh about 5 grams of sodium chloride". Give minimum and maximum amounts of sodium chloride that would satisfy these instructions.

82. ## physics

An object glides on a horizontal tabletop with a coefficient of kinetic friction of 0.55. If its initial velocity is 4.1 m/s, how long does it take for the object to come to rest?

83. ## Chemistry

Calculate the amount of heat required to raise the temperature of a 65-g sample of water from 32∘C to 65∘C. (The specific heat capacity of copper is 4.184 J/g∘C.) Express your answer in Joules.

84. ## Physics

A ball is shot from the ground into the air. At a height of 9.1 m, the velocity is observed to be v = (6.6 + 5.7 ) m/s, with horizontal and upward. (a) To what maximum height does the ball rise? m (b) What total horizontal distance does the ball travel? m

85. ## chem

A 455-g chunk of iron is removed from an oven and plunged into 385g water in an insulated container. The temperature of the water increases from 27 degrees celsius to 89 degrees celsius. If the specific heat of iron is 0.449 J g^-1 degrees Celsius^-1, what

86. ## Algebra

A wire 20 cm long is cut into two pieces. The longer piece is 4 cm longer than the shorter piece. Find the length of the shorter piece of wire

87. ## calculus

Let P= (V^2)R / (R+r)^2 Calculate dP/dr, assuming that r is variable and R is constant.

88. ## Chemistry

Use these answers for questions 4 - 7. (A) 1s2 2s22p5 3s23p5 (B) 1s2 2s22p6 3s23p6 (C) 1s2 2s22p62d10 3s23p6 (D) 1s2 2s22p6 3s23p63d5 (E) 1s2 2s22p6 3s23p63d3 4s2 4. An impossible electronic configuration 5. The ground-state configuration for the atoms of

89. ## physics

A uniform electric field of magnitude 320 V/m is directed in the negative y direction. The coordinates of point A are (-0.300, -0.450) m, and those of point B are (0.650, 0.300) m. Calculate the electric potential difference VB − VA. thanks

90. ## chemistry

Lead is often found in Earth's crust as several lead compounds. Calculate the mass in kilograms of the amount of each of the following lead compounds that contains 4500kg of lead. 1)PbCO3 (cerussite) 2) PbSO4(anglesite)

91. ## Physical science

On a perfect day, you are hovering at low altitude in a hot-air balloon, accelerated neither upward or downward. The total wieght of the balloon, including its load and the hot air in it is 20,000N. Show that the volume of the displaced air is 1700 m3

92. ## Chemistry- Solubility Curves

If 50 grams of water saturated with potassium chlorate at 23*C is slowly evaporated to dryness, how many grams of the dry salt will be recovered? I know that I should know this.. But it has 50 grams of water instead of 100. ): Please, someone tell me how

93. ## chemistry

The number of protons in an anion must always be ________ the number of electrons. the same as We can’t tell. less than greater than

94. ## math

A test had 200 questions .Each correct answer carried 2 marks.Each wrong answer carried -1/2 marks and unanswered question fetched no marks .Ajay attempted all the question in the test and he scored 360 marks.What would his marks be, if for each correct

95. ## Physics

What is the spring constant of a spring that stores 25 J of elastic potential energy when compressed by 6.0 cm from its relaxed length?

96. ## chemistry

In the reaction 2SO2 (g) + O2 (g) 2SO3 (g), which change would cause the greatest increase in the concentration of SO3?

97. ## Chemistry

Calculate the concentrations of S2O8 2-, I-, S2O32 2- in moles per litre of reaction mixture given the following: 20mL of 0.1 M (NH4)2S2O8 added to: 20mL of 0.2M KI 10mL of 0.01M Na2S2O3 5mL 0.2% starch Also, calculate -(delta)S2O8 2- that is, how much

98. ## statistics

a survey is to be conducted to determine the proportion of U.S. voters who support additional aid to African nations to fight poverty and HIV/AIDS. Of the proposed sammple sizes which is the smallest that will guarantee a margin of error of no more than 4%