# david

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

At equilibrium, the concentrations in this system were found to be [N2] = [O2] = 0.100 M and [NO] = 0.500 M. N2(g) + O2(g) 2NO(g) If more NO is added, bringing its concentration to 0.800 M, what will the final concentration of NO be after equilibrium is

2. ## Physics

A 69.5kg football player is gliding across very smooth ice at 2.15m/s . He throws a 0.470kg football straight forward. A) What is the player's speed afterward if the ball is thrown at 16.0m/s relative to the ground? B) What is the player's speed afterward

3. ## physics

Suppose 3 mols of neon (an ideal monatomic gas) at STP are compressed slowly and isothermally to 0.19 the original volume. The gas is then allowed to expand quickly and adiabatically back to its original volume. Find the highest temperature attained by the

4. ## Chemistry

at 25C and 795 torr, carbon dioxide has a solubility of 0.0356 M in water. What is the solubility at 25 C and 2070 torr? ____ M I know that at a given temperature, the solubility of a gas in a liquid is directly proportional to its pressure but how would

5. ## finding c: calc

let f(x)=square root x. if the rate of change of at x=c is twice its rate of change at x=1, then c=? what???? i don't get get it. to begin with, i took the derivative if that helps which is 1/(2*sqrtx) . f'(x) = 1/(2*sqrtx) is correct f'(x=1) = 1/2 The

6. ## Chem

Write a chemical formula. . . Ca2+ and S2-

7. ## Physics

A mass m1 = 3.3 kg rests on a frictionless table and connected by a massless string over a massless pulley to another mass m2 = 4.4 kg which hangs freely from the string. When released, the hanging mass falls a distance d = 0.87 m. 1) How much work is done

8. ## physics

A copper atom has 29 electrons revolving around the nucleus. A copper ball has 4x10^23 atoms. What fraction of the electrons be removed to give the ball a charge of +9.6uC?

9. ## Chemistry

IN my experiment, I was doing a qualitative analysis of Group I and II anions using a flowchart. IN the chart I added 5 drops of 0.1M AgNO3 and several drops of 3M HNO3 to 5 drops of solution and found that a precipitate was formed. Thus it was classified

10. ## Physics

In a repair shop a truck engine that has mass 429 kg is held in place by four light cables (Figure 1) . Cable A is horizontal, cables B and D are vertical, and cable C makes an angle of 37.1∘ with a vertical wall. Tension in cable A is 729 N . a.What is

11. ## Math

in a survey of 290 newspaper readers, 181 of them read the Daily Times, 142 Read the Guardian 117 read punch and each reads at least one of the three papers if 75 read the Daily Times, and the Guardian, 60 read the Daily Times and punch, and 54 read the

12. ## Physics

A person walks the path shown below. The total trip consists of four straight-line paths. Path 1 is 40.0 m due east. Path 2 is 170.0 m due south. Path 3 is 120.0 m 30.0° south of west. Path 4 is 190.0 m 60.0° north of west. At the end of the walk, what

13. ## Math

Eduardo has a red 6-sided number cube and a blue 6-sided number cube. The faces of the cubes are numbered 1 through 6. Eduardo rolls both cubes at the same time. The random variable X is the number on the red cube minus the number on the blue cube. What is

14. ## calc help showed work

If the function f has a continuous derivative on [0,c], the the integral(o to c) of f'(x)dx= a)f(c)-f(0) b)absolute value (f(c)- f(0)) c) f(c) d)f'(x)=c e)f"(c)-f"(0) My work: so the the answer to the integral is f(x) and when find the answer from o t0 c,

15. ## Physics

A tortoise and hare start from rest and have a race. As the race begins, both accelerate forward. The hare accelerates uniformly at a rate of 0.8 m/s2 for 4.4 seconds. It then continues at a constant speed for 13.5 seconds, before getting tired and slowing

16. ## chemistry

When the glucose solution described in part A is connected to an unknown solution via a semipermeable membrane, the unknown solution level rises. Based on this information, what can be said about these two solutions? a.) The unknown solution had the lower

17. ## physics

The length of a simple pendulum is 0.79m and the mass of the particle at the end of the cable is 0.24 kg. The pendulum is pulled away from its equilibrium position by an angle of 8.5 degrees and released from rest. Assume that friction can be neglected and

Estimate a range for each sum. 3.89 + 42.71 + 12.32 I don't understand what to do for "estimating a range".

19. ## statistics

The director of an alumni association for a university wants to look at the relationship between the number of years since graduation and the amount of monetary contribution an alumnus makes to the university. He collects data on 50 alumni who have made

20. ## o-chem

explain how the rate of crystal growth can affect the purity of a recrystallized compound

21. ## CHEMISTRY

A solution of a metal carbonate M2CO3, was prepared by dissolving 7.46 g of the anhydrous solid in water to give 1000cm^3 of solution. 25.0cm^3 of this solution reacted with 27.0cm^3 of 0.100 mol/dm^3 hydrochloric acid. Calculate the relative formula mass

22. ## AP Chemistry

Determine the volumes of 0.10 M CH3COOH and 0.10 M CH3COONa required to prepare 10.0 mL of buffer of each of the following pH values? a. Ph 3.7 b. pH 5.7 C. pH 5.7 I just need to see how to do one of them and I'll understand how to do the rest.

23. ## Math

You are designing a rectangular playground. On your scale drawing, the vertices of the rectangle are (10, –9), (10, –3), and (13, –9). What are the coodinates of the fourth vertex?

24. ## chemistry

In the reaction N2 + 3H2 -> 2NH3, how many grams of NH3 gas would be formed when H2 gas, having a volume of 11.2 liters at STP, reacts with excess N2 gas? Completly confused, thank you very much for your help :)

25. ## Physics

Two identical cars are traveling at the same speed. One is heading due east and the other due north, as the drawing show. What is true regarding the kinetic energies and momenta of the cars?

26. ## Chemistry

Given that the vapor pressure of water is 17.54 torr at 20 C, calculate the vapor-pressure lowering of aqueous solutions that are 2.40 m in (a) sucrose, C12H22O11, and (b) aluminum chloride. Assume 100% dissociation for electrolytes. Sucrose Delta P = __

27. ## Chemistry

The solubility of acetanilide in hot water (5.5 g/100 mL at 100C) is not very great, and its solubility in cold water (0.53 g/100 mL at 0C) is significant. What would be the maximum theoretical percent recovery from the first recrystallization of 0.5 g of

28. ## Geometry

Ray SP bisects angle RST. m

29. ## Chemistry

Suppose you wanted to heat a mug of water (250 mL) from room temperature 25 C to 100 C to make a cup of tea. How much energy (in units of calories and joules) would you need from your microwave?

30. ## physics

A board that is 20 cm wide, 5 cm thick, and 3 m long has a density of 350 kg/m^3. The board is floating partially submerged in water do density 100 kg/m^3. What fraction of the volume of the board is floating above water?;

31. ## Chemistry

What is going on in the hexane layer at the end of the Group I anion experiment? (when color of hexane layer is yellow you have Br- and when it is brown or purple you have I-.) please explain

32. ## Math

Simplify the expression 6P3. I don't know how to solve it so if you could help me with it as well i would really appreciate it.

33. ## Chemistry

8-hydroxyquinoline (Q) can complex and precipitate many metals. A mixture of the aluminium and magnesium complexes weighed 1.0843g (MW=459.43; 312.61). When ignited, the mixture decomposed and left a residue of Al203 (MW 101.96) and MgO (MW 40.304)

34. ## Physics

A road heading due east passes over a small hill. You drive a car of mass m at constant speed v over the top of the hill, where the shape of the roadway is well approximated as an arc of a circle with radius R. Sensors have been placed on the road surface

35. ## Math

A rock is thrown upward from a bridge that is 88 feet above a road. The rock reaches its maximum height above the road 0.67 seconds after it is thrown and contacts the road 3.18 seconds after it was thrown. Define a quadratic function, f, that gives the

36. ## Chemistry

Why do magnesium, phosphorus, and zinc exhibit slightly higher first ionization energies than the general trend within each of their periods?

37. ## Geometry

According to the given information, segment AB is parallel to segment DC and segment BC is parallel to segment AD.. Construct diagonal A C with a straightedge. It is congruent to itself by the Reflexive Property of Equality. ________________. Angles BCA

38. ## MAth

Lily and rose are playing a game, in the game,each player starts with 0 points and the player with the most points at the end win. Lily gains 5 points two times loses 12 points ,and then gains 3 points. Rose loses 3 points two times,loses 1point,gains6

39. ## chemistry

at 20 C the vapor pressure of dry ice is 56.5 atm. if 32 g of dry ice is placed in an evacuated .25 l chamber at a constant temperature of 20 C will all the dry ice sublime

40. ## sum geometric series

what is the sum of geometric infinite series 3/2+ 9/16+ 27/128+ 81/1024=.... i know the formula is S=a/(1-r) my teacher, he usually transforms into a formula of the sum series and finds out a and r.but i don't how to do that. the pattern i saw is 3/2 +

41. ## math

Find the smallest positive integer not relatively prime to 2015 that has the same number of positive divisors as 2015.

42. ## Math

theoretically if you roll a number cube 36 times, how many times would you expect to roll the number one? could you also give me explanation? Thank you. and also answer as fast as possible.

43. ## Chemistry

Calculate the mass of the precipitate formed when 2.27 L of 0.0820 M Ba(OH)2 are mixed with 3.06 L of 0.0664 M Na2SO4.

44. ## Physics

A car moves at 12 m/s for 30.0 seconds. It then accelerates at 1.5 m/s^2 for 8.00 seconds. Finally, it continues on at this top speed for another 12.0 seconds. Calculate the net displacement during the whole time interval.

45. ## Elasticity (Physics)

A tunnel of length L=150m, height H=7.2m, and width w=5.8m (with a flat roof) is to be constructed at a distance d=60m beneath the ground. The tunnel roof is be entirely supported by square steel columns, each with a cross sectional area of 960 cm^2. The

46. ## Science, NATS

Consider the following chemical reaction. Molecular hydrogen and carbon dioxide react to form water and methane. H2+CO2-->H2O+CH4 A)Explain why this equation is not balanced and what law of nature does it break in its current form? B) Astronauts from the

47. ## Math

Joelle earns her regular pay of 7.50 per hour for up to 40 hours a week. for each hour over 40 hours of work in a week, joelle is paid 1.5 times her regular pay. how much does joelle earn for a week in which she works 42 hours?

Hoshi walks 10 meters in 3 seconds. A. What is her walking rate? B. At this rate, how long does it take her to walk 100meters? C. Suppose she walks this same rate for 50sec. How far does she walk? D. Write an equation that represents the distance d that

49. ## Physics

a rocket is launched at an angle of 53 degrees above the horizontal with an initial speed of 75m/s. It moves for 25 seconds along its line of motion with an overall acceleration of 25 m/s^2. What is its maximum height?

50. ## Social Studies

Which of the following correctly pairs a branch of the U.S. government and its power? 1. A. legislative: interprets laws B. executive: makes laws C. executive: enforces laws---- D. judicial: enforces laws 2. Which of the following is an example of the

51. ## math

In 2 minutes, a conveyor belt moves 300 pounds of recyclable aluminum from the delivery truck to a storage area. A smaller belt moves the same quantity of cans the same distance in 6 minutes. If both belts are used, find how long it takes to move the cans

52. ## physics

1.) A vertical spring with a spring constant of 450 N/m is mounted on the floor. From directly above the spring, which is unstrained, a 0.30 kg block is dropped from rest. It collides with and sticks to the spring, which is compressed 2.5 cm in bringing

54. ## physics

A red ball is thrown down with an initial speed of 1.0 m/s from a height of 27.0 meters above the ground. Then, 0.6 seconds after the red ball is thrown, a blue ball is thrown upward with an initial speed of 24.5 m/s, from a height of 0.7 meters above the

55. ## Biology

Compare and contrast indirect versus direct values of biodiversity, and provide examples.

56. ## Statistics

. Two thousand randomly selected adults were asked whether or not they have ever shopped on the internet. The following table gives a two-way classification of the responses obtained. Have shopped Have never shopped Male 500 700 Female 300 500 Suppose one

57. ## science;chem

The hydrolysis of ethyl acetate (CH3COOC2H5) by sodium hydroxide yields ethanol (C2H5OH) and sodium acetate (NaO2CCH3) by the reaction shown, which follows second order kinetics. In an experiment 500 mL of 0.1 M ethylacetate in water is mixed with 500 mL

58. ## Physics

An automobile and a truck start from rest at the same instant, with the automobile initially at some distance behind the truck. The truck has a constant acceleration of 2.15m/s2 , and the automobile an acceleration of 3.47m/s2 . The automobile overtakes

59. ## Physics

A man holds a child on his shoulder while watching a football match.how much work is done if the game lasts for 2hours

60. ## chemistry

A hot recrystallization solution is not filtered unless absolutely necessary.give reason.

61. ## chemistry

Fish-liver oil is a good source of Vitamin A. When 0.1232 g of fish liver oil is dissolved in 500. mL of solvent, an absorbance of 0.724 is recorded. When 0.00167 g of Vitamin A is dissolved in 250. mL of solvent, an absorbance of 1.018 is recorded.

62. ## Chemistry

Barium sulfate, BaSO4 is made by the following reaction. Ba(NO3)2(aq) + Na2SO4(aq)----> BaSO4(s) + 2NaNO3(aq) An experiment was begun with 91.77 g of Ba(NO3)2 and an excess of Na2SO4. After collecting and drying the product, 62.3 g of BaSO4 was obtained.

63. ## Chemistry

Carborundum (silicon carbide) boiling chips are better than calcium carbonate chips in the recrystallization of an unknown,why ?

64. ## History

Use the following statement by Robert Owen to answer the question below: "...but I know that society may be formed so as to exist without crime, without poverty, with health greatly improved, with little if any misery, and with intelligence and happiness

65. ## Physics 1

A textbook of mass 1.95 kg rests on a frictionless, horizontal surface. A cord attached to the book passes over a pulley whose diameter is 0.100 m , to a hanging book with mass 3.08 kg . The system is released from rest, and the books are observed to move

66. ## dbs

Determine the rate of interest at which a sum of money will become 216/125 times the original amount in 1 and a half years, if the interest in compounded half

67. ## Math

A bucket begins weighing 15 pounds, including the sand it holds. The bucket is to be lifted to the top of a 50 foot tall building by a rope of negligible weight. However, the bucket has a hole in it, and leaks 0.1 pounds of sand each foot it is lifted.

68. ## math

Find an angle between 0 degree and 360 degree that is coterminal with given angle. a. 361 degree b. -100 degree c. 1270 degree

69. ## CHEM - ASAPPP

write the equation for the reaction of fecl2 with k3[fe(cn)6]???

70. ## physics

A 52 g mountain climber, start from rest, climbs a vertical distance of 730 m. At top, she is again at rest. In the process, her body generates 4.1*10^6 J of energy via metabolic processes. Her body acts like a heat engine with efficiency ( W/Q_h.) W is

71. ## calc

the volume of a cylindrical tin can with a top and a bottom is to be 16*pi cubic inces. if a minimum amont of tin is to be used to construct the can, what must be the height, in inches, of the can? volume of cyliner is pi*r^2*h do i like take derivitive of

72. ## Science

Ice at 0 degree celcuis is added to 200g of water initially at 70 degree celcuis in a vacuum flask.When 50g of ice has been added and has all melted the temperature of the flask and contents is 40 degree celcuis.When a further 80g of ice has been added and

73. ## algebra 2

The amount of money in an account with continuously compounded interest is given by the formula A=Pe^rt , where P is the principal, r is the annual interest rate, and t is the time in years. Calculate to the nearest hundredth of a year how long it takes

74. ## Maths ( permutation and combination)

a town council plans to plant 12 trees along the centre of a main road.It has 4 hibiscus trees, 6 Jacaranda trees, 2 oleander trees. How many different arrangements of these 12 trees can be made if no hibiscus tree is next to another

75. ## english

Identify the subjects of the following sentences. Jacob's favorite poker game is Texas Hold'em

76. ## probability

Consider an arrival process whose interarrival times are independent exponential random variables with mean 2 (and consequently variance equal to 4), and consider the interarrival interval S seen by an observer who arrives at a fixed time t∗, as in the

77. ## chemistry

Sort these elements into isoelectronic groups. Into three different boxes/sections. Elements: F- O2- Al3+ S2- Ti4+ K+ He Li+ B3+

78. ## finance

Adams Enterprises’ noncallable bonds currently sell for \$1,120. They have a 15- year maturity, an annual coupon of \$85, and a par value of \$1,000. What is their yield to maturity?

79. ## help riemann sums

the expression 1/50 (1/50 +2/50+ 3/50+ .....50/50)is a Reimann sum approximation for (everything in the parantheses is square root except the 1/50 outside the paratheses) the answer has to me the integral form so from looking at the formula in my book i

80. ## chemistry

1. the diameter of a carbon atom is 0.000 000 000 000 154 m. what is the number expressed in the scientific notation? a) 1.54x10^12m b) 1.54x10^-12m c) 1.54x10^10 d) 1.54x10^-10 2. what is the result of multiplying 2.5x10^10 by 3.5x10^-7 a) 8.75x10^-3 b)

81. ## Math

f(x) = tan x / sin x Find the vertical asymptote. Describe its behavior to the left and right of the vertical asymptote.

82. ## math

Kate used 555 grams of wool to knit a sweater, a hat and a scarf. She used 5 times less grams for the hat than for the sweater. She used 5 grams more for the hat than for the scarf. How many grams of wool did she use to knit each item?

83. ## SOCIAL STUDIES

HOW DID THE ICE AGES INFLUENCE HUMAN MIGRATION

84. ## Chemistry

1. You have been given a sample of unknown molarity. Calculate the molarity of a solution which has been prepared by dissolving 8.75 moles of sodium chloride in enough water to produce a solution of 6.22l. 2. You have a sample which consists of 428g sodium

85. ## physics

A rolling ball moves from x1 = 3.2 cm to x2 = -4.2 cm during the time from t1 = 3.8 s to t2 = 6.1 s. What is its average velocity?

86. ## chemistry

Vacuum filtration is avoided when crystals are isolated from a very volatile solvent. why?

87. ## Math

A rooming house has three rooms that contains four beds, three beds and two beds respectively. In how many ways can nine quests be assigned to these rooms? The book says it is 1260. I have no idea how they got this. I know it requires combinations. Could

88. ## Chemistry- Acid-base titration

The indicated endpoint of an acid-base titration seldom occurs at a ph of 7. what determines the ph of the endpoint??

89. ## Physics

You are traveling on an airplane. The velocity of the plane with respect to the air is 110.0 m/s due east. The velocity of the air with respect to the ground is 39.0 m/s at an angle of 30° west of due north. 1) What is the speed of the plane with respect

90. ## Physics

A scaffold of mass 60 kg and length 5.0 m is supported in a horizontal position by a vertical cable at each end.A painter of mass 80 kg stands at a point 1.5 m from one end. (a)Find the tension in the cable nearer to the painter. (b)Calculate the tension

91. ## physica

help A thermally insulated vessel containing 100 grams of ice at 0 degrees Celsius . Water at 55 degrees celsius is poured and after some time , the system reaches the equilibrium at a temperature of 10 degrees Celsius. That amount of water in grams was

92. ## Chemistry

A compound on heating gives a crackling sound, a reddish fume, and a gas which relights a glowing splint. the residue is reddish brown when hot and yellow when cold. What are- 1. the compound? 2. the fume 3. the gas 4. the residue?

93. ## intro to chemistry

A sample of nitrogen has a volume of 50.0L at a pressure of 760mmHg. What is the volume of the gas at each of the following pressures if there is no change in temperature? A. 1500mmHg B. 2.0atm C. 0.500atm

94. ## math

Marta’s math textbook weighs mc017-1.jpg of a pound less than 4 times the weight of the book she is reading for her language arts class. If the weight of the math textbook is mc017-2.jpg pounds, which shows the correct equation and value of x, the weight

95. ## Calculus

Project Setup:You work for a company that manufactures cylindrical steel drums that can be used to transport various petroleum products. Your assignment is to determine the dimensions (radius and height) of a drum that is to have a volume of 1 cubic meter

96. ## elementary statistics

A statistics professor is used to having a variance in his class grades of no more than 100. He feels that his current group of students is different, and so he examines a random sample of midterm grades (listed below). At 0.05 alpha level can it be

97. ## chemistry

The suction of a vacuum filtration apparatus is broken before the vacuum is turned off.give reason.

98. ## chemistry

1)Does the solubility of borax in water increase or decrease as temperature increases? 2)Is the solvation of borax in water an exothermic or endothermic process? please help ive tried asking my ta but i cant understand him. he explains it through this