Wednesday
April 1, 2015

# Posts by sarah

Total # Posts: 4,797

Chemistry
How is the intercept of the Rydberg plot related to the Rydberg constant?
December 7, 2012

Chemistry Check
I just want to make sure I did the following problem right, and don't have to convert any further. What is the frequency of light whose frequency is 6.4 x 10^15 sec^-1? c= wavelength x v wavelength= c/v 3 x10^8 divided by 6.4 x 10^15 =4.69 x 10^-8?
December 7, 2012

Chemistry
The ionization energy of hydrogen is 1313 kJ/mol. Covert this energy to: wavelength (nm) 1/wavelength, reciprocal wavelength (cm^-1) spectral region? (IR, visible, UV, etc.) I know E=hv=hc/wavelength h=6.62 x 10^-34 J-s c= 3x10^8 v=c/wavelength But for some reason trying to ...
December 7, 2012

College Chemistry
Cu(s) + 4HNO3(aq) → Cu(NO3)2(aq) + 2H2O(l) + 2NO2(g) i need the chemical equation and the net ionic equation
December 6, 2012

PHYSICS
A force of 25.0 N acts at an angle of 25° to the horizontal. Find the horizontal and vertical components of the force.
December 5, 2012

Math
I have a 73.3 and that is worth 70% of my mark. My final is worth 30%. What do i need to get on my final to finish with anything over a 70%?
December 5, 2012

easy chemistry
what is the entropy of 10 molecules in a system of 100 boxes?
December 5, 2012

chemistry
what is the pH of the solution formed when 25 mL of 0.173 M NaOH is added to 35 mL of 0.342 M HCl?
December 5, 2012

chemistry
a buffer prepared by mixing equal moles of an acid having Ka=4.5x10^-4 and a salt of its conjugate base has a pH of what?
December 5, 2012

chemistry
the pH of a solution of HIO3 (Ka=1.7x10^-1) and KIO3 is 1.00. what is the molarity of KIO3 if the molarity of HIO3 is 0.025 M?
December 5, 2012

chemistry
what is the pH of the solution formed when 25 mL of 0.173 M NaOH is added to 35 mL of 0.342 M HCl?
December 5, 2012

chemistry
a buffer prepared by mixing equal moles of an acid having Ka=4.5x10^-4 and a salt of its conjugate base has a pH of what?
December 5, 2012

chemistry
the pH of a solution of HIO3 (Ka=1.7x10^-1) and KIO3 is 1.00. what is the molarity of KIO3 if the molarity of HIO3 is 0.025 M?
December 5, 2012

The overall length of a piccolo is 30.6 cm. The resonating air column vibrates as in a pipe that is open at both ends. Assume the speed of sound is 343 m/s. (a) Find the frequency of the lowest note a piccolo can play, assuming the speed of sound in air is 343 m/s. (b) Opening...
December 4, 2012

The overall length of a piccolo is 30.6 cm. The resonating air column vibrates as in a pipe that is open at both ends. Assume the speed of sound is 343 m/s. (a) Find the frequency of the lowest note a piccolo can play, assuming the speed of sound in air is 343 m/s. (b) Opening...
December 4, 2012

The overall length of a piccolo is 30.6 cm. The resonating air column vibrates as in a pipe that is open at both ends. Assume the speed of sound is 343 m/s. (a) Find the frequency of the lowest note a piccolo can play, assuming the speed of sound in air is 343 m/s. (b) Opening...
December 4, 2012

The overall length of a piccolo is 30.6 cm. The resonating air column vibrates as in a pipe that is open at both ends. Assume the speed of sound is 343 m/s. (a) Find the frequency of the lowest note a piccolo can play, assuming the speed of sound in air is 343 m/s. (b) Opening...
December 4, 2012

The overall length of a piccolo is 30.6 cm. The resonating air column vibrates as in a pipe that is open at both ends. Assume the speed of sound is 343 m/s. (a) Find the frequency of the lowest note a piccolo can play, assuming the speed of sound in air is 343 m/s. (b) Opening...
December 4, 2012

Algbra
Marsha must have surgery and she does not have the \$2,700 cash necessary for the operation. Talking to an administrator at the hospital, she finds that it will accept MasterCard, VISA, and Discover credit cards. All of these credit cards have an APR of 13%, so she figures that...
December 4, 2012

Algbra
A car dealer will sell you the \$16,650 car of your dreams for \$3,290 down and payments of \$331.97 per month for 48 months. What is the APR? (Round your answer to the nearest tenth of a percent.) I keep getting the wrong answer. I get 26.1
December 4, 2012

Trigonometry
Find all solutions between 0 and 2pi to tan(x)=-Squareroot3 exactly.
December 3, 2012

Physics
Two resistors of equal resistance are connected in series with each other and are connected to a battery that produces a potential difference of 8 V. If the current is 0.2 A what is the value of each resistance?
December 2, 2012

Chemistry
The compound CH3F has van der Waals constants a = 5.009 atm•L2 /mol 2 and b = 0.0562 L/mol. Using both the ideal gas law and van der Waals’s equation, calculate the pressure expected for 25 mol of CH3F gas in a 5.00-L container at 75 °C. no idea how to even start...
December 1, 2012

Chemistry
If you place 10.0 L of propanol (C3H8O) in a sealed room that is 7.5 m long, 3 m wide, and 3 m high, will all the propanol evaporate? If some liquid remains, how much will there be? The vapor pressure of propanol is 10.7 torr at 25 °C, and the density of the liquid at this...
December 1, 2012

Chemistry
Dimethylamine burns in oxygen according to the following equation: 4 C2H7N + 15 O2 → 8 CO2 + 14 H2O + 2 N2 (a) How many liters of O2 at 35 °C and 0.840 atm will be needed to burn 7.70 L of C2H7N at 35 °C and 0.840 atm? (b) How many liters of CO2 at 35 °C and ...
December 1, 2012

Chemistry
= 728/(2.807)(0.08206)(291.15) =10.855 g ?
December 1, 2012

Chemistry
What is the molar mass of a compound if a gaseous sample has a density of 2.807 g/L at 18 °C and 728 torr?
December 1, 2012

Physics !:(
A carbon dioxide laser is an infrared laser. A CO laser with a cavity length of 48.6cm oscillates in the m=100,000.0 mode. What is the wavelength of the laser beam? b). What is the frequency of the laser beam?
November 30, 2012

Calculus
Find the derivative of y = x^x
November 28, 2012

Calculus
Find the maximum volume of a cylindrical tin that has a total surface area of 600pi cm^2.
November 28, 2012

Math
November 28, 2012

science
In cattle, red hair and white hair are codominant. Cattle with both white hair and red hair are what? please help! thanks!
November 27, 2012

Physics
A toy is attached to the cieling by a string. As the toy flies around in a horizontal circle with a radius 45 cm, the string makes an angle of 60 degrees with the cieling. What is the speed of the toy?
November 27, 2012

physics
Suppose the roller coaster in Fig. 6-41 (h1 = 34 m, h2 = 10 m, h3 = 30) passes point 1 with a speed of 1.60 m/s. If the average force of friction is equal to one fourth of its weight, with what speed will it reach point 2? The distance traveled is 60.0 m.
November 26, 2012

How can you use 4x7 to find 8x7? find the product. I dont understand this how can i expect my 3rd grader to understand.
November 26, 2012

Physics HELP!!
a). The displacement of a wave travelling in the positive x-direction is D(x,t)=(5.94cm)sin(1.18x-132.6t), where x is in meters and t is in seconds. What is the frequency? b). What is its wavelength? c).What is the speed of the wave?
November 24, 2012

A jet airplane has an intensity of 97.7W/ m^2 when heard at a distance of 30.0m. What is the maximum sound intensity heard by a person on the ground when the airplane is 10100m overhead?
November 24, 2012

A microphone has an area of 3.0cm^2. It receives during a 6.00s time period a sound energy of 1.0x10-11J. What is the intensity of the sound? b). Using the intensity in the previous question, what is the variation of pressure in the sound wave if the speed of sound is 343m/s ...
November 24, 2012

Spanish
whenever the word 'que' is used in a sentence and a verb follows it, the verb will always be in the unconjugated form. Tenemos que IR al parque. tienen que ESTUDIAR. tengo que HACER mi tarea.
November 21, 2012

Physics
For a certain transverse wave, the distance between two successive crests is 4.48m, and 13 crests pass a given point along the direction of travel every 5.97s. Calculate the wave speed!
November 21, 2012

Physics HELP!!
Earthquakes are essentially sound waves travelling through the earth. They are called seismic waves. Because the earth is solid, it can support both longitudinal and transverse sismic waves, which travel at different speeds. The speed of longitudinal waves, called P waves, is ...
November 21, 2012

Physical
It is experiment electric resistivty For the pencil line
November 20, 2012

Physical
The pencil line is made out of carbon atoms. Assuming that the average diameter of a carbon atom is 3.49x10^-10m, how many atoms thick is the pencil?
November 20, 2012

Physics
Football is kicked up into the air with a velocity of 20m/s. a. Determine the time the football is in the air. b. Determine the maximum height the football would reach. c. As the ball is kicked it encounters a weird horizontal wind that gives it a velocity of 5m/s. Determine ...
November 19, 2012

Physics
part 1 of 3: A hawk flies in a horizontal arc of radius 9.9 m at a constant speed of 4.8 m/s. Find its centripetal acceleration. Answer in units of m/s^2. part 2 of 3: It continues to fly along the same horizontal arc but increases its speed at the rate of 1 m/s^2. Find the ...
November 19, 2012

Physics URGENT!!!
A spring of negligible mass stretches 2.14 cm from its relaxed length when a force of 8.40 N is applied. A 1.300 kg particle rests on a frictionless horizontal surface and is attached to the free end of the spring. The particle is displaced from the origin to x=5.00 cm and ...
November 19, 2012

algebra
Find the cost of a home in 20 years, assuming an annual inflation rate of 5%, if the present value of the house is \$260,000.
November 18, 2012

chemistry... HELP !!!!!!!
The average bond enthalpy for C__H is 413 kJ/mol. In other words, 413 kJ of energy is required to break a mole of CH into atoms: CH (g) ----> C(g) + H(g) delta H= 413 kJ Using this information, and enthalpy of C6H6=5535kJ, calculate the enthalpy change of the reaction: C6H6...
November 18, 2012

CHEMISTRY
Consider a 58.4 g sample of H2O(g) at 125°C. What phase or phases are present when -162 kJ of energy is removed from this sample? Specific heat capacities: ice, 2.1 J g-1 °C-1; liquid, 4.2 J g-1 °C-1; steam, 2.0 J g-1 °C-1, ΔHvap = 40.7 kJ/mol, ΔHfus...
November 17, 2012

CALCULUS
Find the length of the curve: y=ln(1-x^2), 0<_x<_1/2
November 16, 2012

CALCULUS
Let R be the region bounded by y=e^x, y=2. and the y-axis. Find the volume of the solid obtained by rotating the y-axis.
November 15, 2012

trig
given that 1/2pi<theta<pi and sin theta=1/5, use appropriate trigonometric formulas to find the exact values of the following (i) cos(2theta) (ii) cos theta (iii) sin(2theta)
November 15, 2012

PHYSICS
At what temperature would the rms speed of a nitrogen atom equal the following speeds? (Note: The mass of a nitrogen atom is 2.324 10-26 kg.) (a) the escape speed from Earth, 1.12 104 m/s _____K (b) the escape speed from the Moon, 2.37 103 m/s _____K
November 14, 2012

PHYSICS
An air bubble has a volume of 1.65 cm3 when it is released by a submarine 105 m below the surface of a lake. What is the volume of the bubble when it reaches the surface? Assume the temperature and the number of air molecules in the bubble remain constant during its ascent. ...
November 14, 2012

PHYSICS
One mole of oxygen gas is at a pressure of 5.25 atm and a temperature of 29.5°C. (a) If the gas is heated at constant volume until the pressure triples, what is the final temperature? ____°C (b) If the gas is heated so that both the pressure and volume are doubled, ...
November 14, 2012

PHYSICS
The average coefficient of volume expansion for carbon tetrachloride is 5.81 10-4 (°C)−1. If a 42.5-gal steel container is filled completely with carbon tetrachloride when the temperature is 10°C, how much will spill over when the temperature rises to 26.5°C...
November 14, 2012

PHYSICS
The Trans-Alaskan pipeline is 1300 km long, reaching from Prudhoe Bay to the port of Valdez, and is subject to temperatures ranging from -72°C to +38°C. (a) How much does the steel pipeline expand due to the difference in temperature? (The coefficient of linear ...
November 14, 2012

PHYSICS
Lead has a density of 1.13 104 kg/m3 at 0°C. (a) What is the density of lead at 86°C? ___kg/m3 (b) Based on your answer to part (a), now consider a situation in which you plan to invest in a gold bar. Would you be better off buying it on a warm day? Yes or No Explain.
November 14, 2012

Chemistry
What is the wavelength in Angstroms of radiation that has a frequency of 4.00 x 10^14 s-1? I tried the equation wavelength= constant / frequency. And the fact that 1 Angstrom = 1x 10^-10 m, but I don't see how the correct answer turns out to be 7.5 x 10^3
November 14, 2012

Chemistry
What is the energy in Joules of a mole of photons of microwave light having a frequency typical of microwave? (frequency = 3.0 x 10^9 Hz) I tried using the equation E= h x frequency, but I ended up with the answer 1.98 x 10^-24 instead of the correct answer 1.2 J, so there ...
November 14, 2012

Chemistry
What is the total volume of gases produced at 819 K and 1. atm pressure when 320 g of ammonium nitrite undergoes the following decomposition reaction? NH4NO2 --------> N2(g) + 2H2O(g)
November 14, 2012

Chemistry
Thanks so much, I would of never figured out that out myself past the empirical formula since I forgot about the 22.4L factor. The molar mass turns out to be 70, and since the only answer I was given that adds up to 70 is C5H10, it's an easy pick. Pentane!
November 14, 2012

Chemistry
An unknown gaseous hydrocarbon consists of 85.63% carbon by mass. A 0.335 g sample of the gas occupies a volume of 0.107 L at STP. What is the identity of the gas?
November 14, 2012

Chemistry
A 3.80 L cylinder contains 6.83g of methane, CH4, at a pressure of 3320 mmHg. What is the temperature of the gas? I know you use the formula PV= nRT, but I can't seem to get two sides equal each other, thus having the wrong temp. My guess is that I have to change mmHg to a...
November 14, 2012

Physics HELP!!
Four masses are connected by 27.1cm long, massless, rigid rods. If massA=237.0g, massB=511.0g, massC=257.0g, and massD=517.0g, what are the coordinates of the center of mass if the origin is located at mass A? ^ I already got this part: x coordinate- 13.78 cm y coordinate- 13....
November 13, 2012

Physics
A street lamp weighs 160 N. It is supportedequally by two wires that form an angle of 119 with each other. What is the tension of each of these wires? Answer in units of N
November 12, 2012

Chemistry
A 3.80 L cylinder contains 6.83 g of methane, CH4, at a pressure of 3320 mmHg. What is the temp. Of the gas? I mainly have problems being able to tell which gas law equation I need to use when asked these types of questions and then being able to rearrange the equation to find...
November 12, 2012

Physics
A hiker who weighs 834N, is strolling through the woods and crosses a small horizontal bridge. The bridge is uniform, weighs 3520N, and rests on two concrete supports at each end. He stops one-fifth of the way along the bridge. What is the magnitude of the force that a ...
November 12, 2012

A uniform plank of length 5.0 m and weight 231N rests horizontally on two supports, with d = 1.34m of the plank hanging over the right support. To what distance, x, can a person who weighs 477N walk on the overhanging part of the plank before it just begins to tip?
November 12, 2012

Physics B
Part 1 A 36 kg girl is standing on a 65 kg plank. The plank, originally at rest, is free to slide on a frozen lake, which is a ﬂat, frictionless supporting surface. The girl begins to walk along the plank at a constant speed of 1.89 m/s to the right relative to the ...
November 12, 2012

Algebra
2x+3=-2x+5 I think the answer is 8 ______________________________ 1-2x-5=4x+2 2x=8? X=4? I doubt I got this right
November 12, 2012

Algebra
3x + 7= -x - 1 -3x=x-(6-2x) 1-2x-5=4x+2 2x+3=-2x+5 I cant remember the steps to evaluate.
November 12, 2012

Andrew guess what, I was a tid bit busy. So spare the tude. thanks Bobpursley.
November 11, 2012

This is my HW problem; I'm thinking of a number. When I double my number, subtract five, and then add my original number, I get one. What's my number?
November 11, 2012

physics
A cook holds a 2.66-kg carton of milk at arm's length (see the figure below). What force B must be exerted by the biceps muscle? (Ignore the weight of the forearm. State the magnitude of the force B.)
November 11, 2012

physics
Suppose a 34.5-kg child sits 1.17 m to the left of center on the same seesaw as the problem you just solved in the PRACTICE IT section. A second child sits at the end on the opposite side, and the system is balanced.
November 9, 2012

physics
k(.005m)=((8.99X10^9)*(2.70X10^-6)*(8.60X10^-6))/(.09m)^2 k=5.15X10^3
November 7, 2012

economics
1. When the government attempts to cover large deficits by creating more money, what is the probable result called? (1 point) (0 pts) government borrowing (1 pt) hyperinflation (0 pts) excess currency (0 pts) full employment 1 /1 point 2. What is one of the major problems ...
November 6, 2012

Calculate the interest on a \$1700 credit card bill that shows a 22% APR, using the average daily balance method. Assume you sent a payment of \$375 on the first day of a month that has 30 days and it takes 5 days for this payment to be received and recorded. Round to the ...
November 6, 2012

MATH
you mean 1700x0.02x1/12=31.16? that is not the right answer though :(
November 6, 2012

MATH
Calculate the interest on a \$1700 credit card bill that shows a 22% APR, using the average daily balance method. Assume you sent a payment of \$375 on the first day of a month that has 30 days and it takes 5 days for this payment to be received and recorded. Round to the ...
November 6, 2012

A 10.0 kg cylinder rolls without slipping on a rough surface. At an instant when its center of gravity has a speed of 16.0 m/s, determine (a) the translational kinetic energy of its center of gravity.(b) the rotational kinetic energy about its center of gravity, and (c) its ...
November 6, 2012

chemistry
Given the reaction: H2SO4 = 2NaOH -> NaSO4 = 2H20. Determine the # of moles of sulfuric acid id needed to completely react with 2.3 L of 0.5 M of NaOH. Then determine the concentration of the solution if 3.0 L of it are used instead.
November 4, 2012

chemistry
Given the reaction: H2SO4 = 2NaOH -> NaSO4 = 2H20. Determine the # of moles of sulfuric acid id needed to completely react with 2.3 L of 0.5 M of NaOH. Then determine the concentration of the solution if 3.0 L of it are used instead.
November 4, 2012

Physics
A crane lifts the 22000kg steel hull of a ship out of the water. Determine the tension in the crane's cable when the hull is submerged in the water. Determine the tension when the hull is completely out of the water.
November 3, 2012

Physics
A 19cm radius air duct is used to replenish the air of a room 9.2m x 6.0m x 4.0m every 18min . How fast does air flow in the duct?
November 3, 2012

Physics
What is the total force on the bottom of a swimming pool 27.5m by 9.0m whose uniform depth is 1.9m? physics What is the absolute pressure on the bottom of a swimming pool? What will be the pressure against the side of the pool near the bottom?
November 3, 2012

physics
a drunken motorist who is moving at a constant velocity of 90 km/h passes a stationary police patrol car. The patrol car immediately gives chase at a constant acceleration and catches up with the motorist after a distance of 10 km. Calculate the time taken by the patrol car to...
November 2, 2012

Physics
A car is stopped at a stoplight. When the light turns green, it accelerates with a constant acceleration of 2.5 m/s^2. At the same instant, a truck passes the car in the same direction with a constant velocity of 15 m/s. how long until the car catches the truck?
November 1, 2012

math
how many possible combinations are there to make \$1.55 using a dollar, dimes and pennies?
November 1, 2012

math
how do i find the equivalent decimal for 2 3/4
November 1, 2012

PHYSICS HELP-multiple choice
A red ball with a velocity of +3.0 m/s collides head-on with a yellow ball of equal mass moving with a velocity of -2.0 m/s. What is the velocity of the red ball after the collision? A. zero. B. -2.0 m/s. C. +3.0 m/s. D. +2.5 m/s. E. +5.0 m/s. I think zero but need a second ...
October 31, 2012

Physics
A(n) 95.7 kg boxer has his first match in the Canal Zone with gravitational acceler- ation 9.782 m/s2 and his second match at the North Pole with gravitational accelera- tion 9.832 m/s2. a) What is his mass in the Canal Zone? Answer in units of kg b) What is his weight in the ...
October 30, 2012

Physics
A(n) 95.7 kg boxer has his first match in the Canal Zone with gravitational acceler-ation 9.782 m/s2 and his second match at the North Pole with gravitational accelera- tion 9.832 m/s2.
October 30, 2012

Computer Science
public class RandomPhoneNumber { public static void main(String[] args) { int num1=(int)(Math.random()*7); int num2=(int)(Math.random()*7); int num3=(int)(Math.random()*7); int set1=(int)(100+Math.random()*642); int set2=(int)(1000+Math.random()*8000); System.out.println("...
October 30, 2012

Assume you are agile enough to run across a horizontal surface at 11.60 m/s on an airless spherical asteroid of uniform density 1.0x103 kg/m3, independently of the value of the gravitational field. To launch yourself into orbit by running, what would be (a) the radius? (b) the...
October 29, 2012

Chemistry
a silver coin has a mass of 2.50g and is analysed for silver by dissolving in dilute nitric acid, and precipitating silver as solid AgCl and weighing this. if the percipitat weighs 2.99g what percentage of silver is the coin?
October 29, 2012

Geometry
Which statement about a figure ABCD would always be true ?
October 28, 2012

Organic Chemistry
I think I got something: there should be 2 Rf values, since there are two components; maybe the spot was not concentrated enough. So the way to fix the error would be to make the spot bigger. Is this right?
October 28, 2012

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