Friday

July 1, 2016
Total # Posts: 3,000

**history**

what event caused the greek city- states to put aside their differences.
*April 16, 2012*

**physics**

Two waves traveling on a string in the same direction both have a frequency of 100 Hz, a wavelength of 2cm and an amplitude of .02 m. What is the amplitude of the resultant wave if the original waves differ in phase (a) by Pi/6 and (b) by Pi/3
*April 16, 2012*

**chem**

Hey could you please help me. Why would K2CO3 be a better drying agent than Na2SO4 when drying out water from clohexanol?
*April 15, 2012*

**Math**

what is the median of the numbers 3,6,10,12,27,62
*April 15, 2012*

**physics energy**

A potential function is given by U(x) = 18 x^2. What will be the acceleration (in meters/second ^2) of a 8.00 kg mass, when it is at the position x = 0.500 m?
*April 13, 2012*

**chemistry**

What is the limiting reactant of 4000 grams of heptane is combusted with 7000 grams of oxygen?
*April 13, 2012*

**Pre-calculus**

Use the remainder theorem to find which of the following is not a factor of x3 + 12x2 + 47x + 60 the answer is x-5 but idk why
*April 6, 2012*

**trig**

simplify cox^2x-cos^4x
*April 5, 2012*

**Chemistry**

? lost- what chart?
*April 5, 2012*

**Chemistry 2**

(.032^2)x(.016^-1)^2 =4
*April 5, 2012*

**Chemistry 2**

i still dont get this
*April 5, 2012*

**Mechanics for A-level **

An object of mass 50kg rests on a rough plane inclined at an angle z to the horizontal. It is supported in this position by a light string parallel to the plane which is attached to the object and fixed to a point at the top of the plane. The string has a breaking strain of ...
*April 5, 2012*

**finite math**

Determine whether each system of linear equations has a)one and only one solution, b)infinitely many solutions, or c) no solution 2x-4y=5 3x +2y=6
*April 3, 2012*

**physics**

A uniform horizontal wire with a linear mass density of 0.48 g/m carries a 1.9 A current. It is placed in a constant magnetic field, with a strength of 3.5 10-3 T, that is horizontal and perpendicular to the wire. Neglect the magnetic field of the Earth. (a) As the wire moves ...
*April 1, 2012*

**Mechanics (A level), Please help**

Call the length of string below point B as h, then diagonal of triangle = a - h. angle to vertical of string = theta T + Tcostheta = W use pythagoras to find h (a - h)^2 = b^2 + h^2 so h = (a^2 - b^2)/2a and costheta = h/(a-h) = (a^2 - b^2) /(2a(a - [(a^2 - b^2)/2a] ) which ...
*April 1, 2012*

**physics**

A +5.7C X 10 to the -6 power point charge is on the x-axis at x=-3.0m,and a +2.0C X 10 to the -6 power point charge is on the x-axis at x=+1.0m.Determine the net electric field (magnitude and direction) on the y-axis at y=+2.0m.
*March 30, 2012*

**Government**

The Anti-federalists were against ratification of the constitution mostly because
*March 29, 2012*

**science**

Examine the obvious environmental impacts as well as significant social and physical ramifications of urban sprawl. What is the relationship between landscape and psychological well being? After defining this relationship, discuss how the presence or absence of natural beauty ...
*March 29, 2012*

**science**

Give examples of how humans have increased their food supply and what effects these methods have on the environment overall.
*March 29, 2012*

**chemistry**

how does the addition of a nonvolatile solute affect the vapor pressure of the solvent into which it is dissolved?
*March 27, 2012*

**chemistry**

2- A 0.310 M solution of a weak acid, HX, has a pH of 2.53 a. Find the [H+] and the percent ionization of nitrous acid in this solution. b. Write the equilibrium expression and calculate the value of Ka for the weak acid. c. Calculate the pH of the solution formed by adding 10...
*March 25, 2012*

**chemistry**

thank you!
*March 25, 2012*

**Chemistry**

need more help
*March 25, 2012*

**Chemistry**

need more help
*March 25, 2012*

**math**

The space station is going 17500 mph as it orbits the earth. How long will it take to orbit 1 time if the earths diameter is 7926 miles and the space station orbits at 240 miles above the earth.
*March 25, 2012*

**Science**

How many milliliters of water at 20.0 °C are formed in the combustion of 25.0 g of a methanol–propanol mixture that is 62.5% methanol by mass? Assume there is an excess of oxygen available.
*March 22, 2012*

**chemistry**

120.g NO
*March 21, 2012*

**chemistry**

How man grams of nitrogen monoxide are needed to react with adequate oxygen to produce 89.6 L of nitrogen dioxide
*March 21, 2012*

**Chemistry**

100 J
*March 20, 2012*

**AQA Mechanics (M1), Statics and forces,please help**

The diagram shows a cylinder of mass 20 kg lying at rest on two smooth planes inclined at angles of 40 degree and 50 degree to the horizontal. Calculate the reaction force exerted by the planes on the cylinder. For digram, please click the following link
*March 19, 2012*

**chemistry**

If HClO2 is a stronger acid than HF, which is stronger than HOCl, then the order of strengths of the conjugate bases of these acids is ______ < _____ < _____ a) ClO- < F- < ClO2- b) ClO2- < ClO- < F- e) F- < ClO2- < ClO- c) ClO- < ClO2- < F- d) ...
*March 17, 2012*

**chemistry**

The Ka for HOBr is 2.4 x 10-9. Thus, you can report the pKb for OBr– as a) 4.2 x 10-6 b) 9.62 c) 5.38 d) 8.62 e) 1.38 help!
*March 17, 2012*

**chemistry**

Which salt below will dissolve in water to yield an acidic solution? a) NaNO2 b) K C§¤O4 c) NH4NO3 d) Na2CO3 e) Mg Br2 help!
*March 17, 2012*

**chemistry**

The approximate pH of a 3.0 x 10-3 M solution of the strong acid H2SO4 is a) 3.5 b) 3.0 c) 2.5 d) 2.2 e) -3.0 how do you do this?
*March 17, 2012*

**chemistry**

The ion HPO4–2 has both a conjugate base as well as a conjugate acid. The conjugate base of this ion is (1) while the conjugate acid is (2). a) (1) = H2PO4– (2) H3PO4 b) (1) = PO4– (2) H2PO4+ c) (1) = PO4–3 (2) H2PO4– d) (1) = HPO5–3 (2) HPO3–...
*March 17, 2012*

**chemistry**

Which of the following is a Bronsted-Lowry base but not a Lewis base? a) H2O c) CN– e) all choices are both a B/L and Lewis base. b) CO3–2 d) NH3 need help deciding
*March 17, 2012*

**chemistry**

Which of the following is not amphiprotic? a)H2O c)NH4+ e)all choices are amphiprotic b)HSO4 – d)H2PO4– need help!
*March 17, 2012*

**english**

In The Secret, the secret is found in a a conversation. b letter. c line of poetry. d newspaper column. I think a
*March 13, 2012*

**chemistry**

Using this data, 2 NO(g) + Cl2(g) == 2 NOCl(g) Kc = 3.20 X 10-3 NO2(g) == NO(g) + ½ O2(g) Kc = 3.93 calculate a value for Kc for the reaction, NOCl (g) + ½ O2 (g) == NO2 (g) + ½ Cl2 (g) A. 20.2 B. 2.06 X 10-4 C. 4.49 D. 4.84 X 10-3 E. 0.223 eliminated down...
*March 12, 2012*

**chemistry**

Using this data, 2 NO(g) + Cl2(g) == 2 NOCl(g) Kc = 3.20 X 10-3 NO2(g) == NO(g) + ½ O2(g) Kc = 3.93 calculate a value for Kc for the reaction, NOCl (g) + ½ O2 (g) == NO2 (g) + ½ Cl2 (g) A. 20.2 B. 2.06 X 10-4 C. 4.49 D. 4.84 X 10-3 E. 0.223 eliminated down...
*March 12, 2012*

**physics**

A child moves with a speed of 5.40 m/s when positioned 14.0 m from the center of a merry-go-round. Calculate the net force (in newtons) exerted on the child, whose mass is 26.0 kg.
*March 12, 2012*

**chemistry**

when you reverse it do you get a negative?
*March 12, 2012*

**chemistry**

Using this data, 2 NO(g) + Cl2(g) == 2 NOCl(g) Kc = 3.20 X 10-3 NO2(g) == NO(g) + ½ O2(g) Kc = 3.93 calculate a value for Kc for the reaction, NOCl (g) + ½ O2 (g) == NO2 (g) + ½ Cl2 (g) A. 20.2 B. 2.06 X 10-4 C. 4.49 D. 4.84 X 10-3 E. 0.223 eliminated down...
*March 12, 2012*

**Math**

A bag has 4 red, 6 white, and 9 blue marbles. How many ways can 5 marbles be selected if 2 are one color, and 3 are another color?
*March 12, 2012*

**PHi103**

The truth table for a valid deductive argument will show
*March 11, 2012*

**math**

(4.35E-2 - x)(7.56E-2 -x ) ============================ (0.324 + 2x)2 Rearrange to get an expression of the form ax2 + bx + c = 0 and use the quadratic formula (solve for x. This gives: x = 1.05E-2, 0.143 basically i understand they use the quadratic equation but how did they...
*March 10, 2012*

**chemistry this is confusing to me please help**

Screw u
*March 9, 2012*

**chemistry this is confusing to me please help**

HAHA no
*March 9, 2012*

**english 11**

just took it. Joyce has the right answers.
*March 9, 2012*

**english 11**

a b c d
*March 9, 2012*

**physics**

a 25000000 gr rocket is propelled from rest by an engine that produces a 312500 kgm/s2 for 1.375s A) What is the sleds acceleration? B) What is the velocity after 1.375s?
*March 7, 2012*

**Math :(**

please answer......
*March 6, 2012*

**Math :(**

A rectangular pyramid with the base of 12 feet by 8 feet need to be filled with balloons. if the pyramid 16 feet tall, how much space is available for the balloons?
*March 6, 2012*

**math**

the outlier is 7 and the outlier is a number away from all the other ones,which in this case is 7.
*March 6, 2012*

**math**

Jean has 4 times as many marbles as Peter. If Jean gave 18 marbles to Peter, they would then have the same number of marbles. How many marbles does each have?
*March 6, 2012*

**Chemistry**

How many moles of nitric acid will be produced when .51 mole of dinitrogen pentoxide reacts
*March 5, 2012*

**7th grade math**

yes,Pi is an irrational number.
*March 5, 2012*

**math**

Determine the slope of a line passing through the points (2, 9) and (0.66, 9).
*March 5, 2012*

**physics**

Jabdbal
*March 5, 2012*

**6th grade science**

How do the surface proteins on a virus help it to invade a host cell?
*March 4, 2012*

**Math**

Parallel lines have the same slope so the slope of 3x-4y+5 =0 is y=(-3x-5)/-4 slope =3/4 therefore the y=(n-2)x+12 must have a slope of 3/4 so n-2=3/4 n=2.75 If the lines are perpendicular they have negative reciprocal slopes therefore n-2= -4/3 n=2-4/3 or 2/3
*March 3, 2012*

**algebra**

There are three important numbers coming from the factors, 0, -1, and 3 test using numbers around those numbers. Using -2 because it is less than -1 (-2)(-2+1)(-2-3) =-10 which is < 12 Using -.5 because it is between -1 and 0 (-.5)(-.5+1)(-.5-3)=.875 which is <12 Using 1...
*March 3, 2012*

**Physics help?**

A 170 -pF capacitor is connected in series with an unknown capacitance, and as a series combination they are connected to a battery with an emf of 25.0 V. If the 170 -pF capacitor stores 135 pC of charge on its plates, what is the unknown capacitance?
*March 3, 2012*

**maths**

Do the same thing you did before using -1/2 for x. (2x+1=0 and solve for x) Then you will have two equations and two unknowns and you can solve for p
*March 3, 2012*

**math**

x= total marbles x-(1/4)x what he had after 1st round (x-(1/4)x)-1/3(x-(1/4)x) what he had left after 2nd (x-(1/4)x)-1/3(x-(1/4)x)-1/2((x-(1/4)x)-1/3(x-(1/4)x)) what he had left after 3rd round which equals 2 (the one he gave to Shavana and the one he kept) (x-(1/4)x)-1/3(x-(1...
*March 3, 2012*

**Math**

When raising to a power multiply the exponents. 8.8*10^25
*March 2, 2012*

**math**

I do
*March 1, 2012*

**math 2nd grade**

francisco (:
*February 29, 2012*

**3 grade math**

You body consist of 7/10 water. Is more than 1/2 your body water? Explain
*February 29, 2012*

**5th grade Math**

-3+5*(2(-6))=37
*February 29, 2012*

**Trig**

A pilot is flying over a straight highway. He determines the angles of depression to two mileposts, 6.7 mi apart, to be 36° and 41°, as shown in the figure
*February 29, 2012*

**One Trigonometry Question Please Help!**

8 1/2 inches long into 1/2 inches long will be how many short pecies
*February 28, 2012*

**Math**

Words
*February 27, 2012*

**Mathematics**

What percentage is 2/27?
*February 27, 2012*

**Physics**

A 73kg sprinter, starting from rest, reaches a speed of 7.0 m/s in 1.8s, with a negliable effect due to air resistance. The sprinter then runs with the remained of the race at a steady speed of 7.0 m/s under the influence of a 35-N force due to air resistance. What is the ...
*February 27, 2012*

**Math**

It equauls 2sinx
*February 25, 2012*

**Math**

How do I solve: sqrt(3)tanx= I need to use the identity tanx=sinx/cosx Thanks
*February 25, 2012*

**chemistry**

If the reaction Cl2 (g) + O3 (g) = Cl2O (g) + O2 (g) occurred in just two steps, what would be the overall order of the reaction be? a. 1 b. 2 c. 3 d. 4 e. not possible to determine from the information given help
*February 25, 2012*

**chemistry**

The equation A + 2 B = C + D describes an elementary reaction, which takes place in a single step. Thus, the rate law must be a. rate = k(A]2 b. rate = k(B]2 c. rate = k(A][B] d. rate = k(A][B]2 e. none of the above represents the rate law for this elementary reaction. help
*February 25, 2012*

**chemistry**

The decomposition of hydrogen peroxide in solution and in the presence of iodide ion was studied in laboratory, and the following mechanism proposed based on the experimental data. H2O2 + I - = H2O + IO - (slow) H2O2 + IO - = H2O + O2 + I - (fast) Which one of the following ...
*February 25, 2012*

**chemistry**

A particular reaction has an activation energy of 51.6 kJ/mol-rxn. How much faster is the reaction at 50 degrees C versus 25 degrees C? a. 2 times b. 5 times c. 3 times d. half as fast d. 20% as fast help No one has answered this question yet.
*February 25, 2012*

**chemistry**

For a one step reaction, the activation energy for the forward reaction is 40.0 kJ/mol and the enthalpy of reaction is -20.0 kJ /mol. Which statement below is true? a. The activation energy of the forward reaction would be affected to a greater extent than the activation ...
*February 25, 2012*

**chemistry**

If the reaction Cl2 (g) + O3 (g) = Cl2O (g) + O2 (g) occurred in just two steps, what would be the overall order of the reaction be? a. 1 b. 2 c. 3 d. 4 e. not possible to determine from the information given
*February 24, 2012*

**chemistry**

A catalyst alters the rate of a reaction by a. changing the products in the reaction. b. increasing the activation for the reaction. c. always providing a surface on which the molecules react. d. providing an alternate pathway for the reaction. e. increasing the concentrations...
*February 24, 2012*

**chemistry**

The equation A + 2 B = C + D describes an elementary reaction, which takes place in a single step. Thus, the rate law must be a. rate = k(A]2 b. rate = k(B]2 c. rate = k(A][B] d. rate = k(A][B]2 e. none of the above represents the rate law for this elementary reaction.
*February 24, 2012*

**chemistry**

The decomposition of hydrogen peroxide in solution and in the presence of iodide ion was studied in laboratory, and the following mechanism proposed based on the experimental data. H2O2 + I - = H2O + IO - (slow) H2O2 + IO - = H2O + O2 + I - (fast) Which one of the following ...
*February 24, 2012*

**chemistry**

The reaction: A + 3 B = D + F was studied and the following mechanism was finally determined A + B = C (fast) C + B = D + E (slow) E + B = F (very fast) The step with largest activation energy is a. the first step b. the second step c. the third step d. none of the steps has ...
*February 24, 2012*

**chemistry**

For a particular chemical reaction, the rate constant at 30.0 °C is 1.38 X 10-4 L mol-1 s-1, while the value at 49.0 °C is 1.21 X 10-3 L mol-1 s-1 . What is the activation energy for this reaction? a. 92.8 kJ b. 200 kJ c. 40.4 kJ d. 343 kJ e. 56.4 kJ ln 1.38x 10 -4 / 1...
*February 24, 2012*

**chemistry**

For a certain chemical reaction, the rate constant at 250.0 °C is 0.00383 s-1 and the activation energy is 22.40 kilojoules. Calculate the value of the rate constant at 335.0 °C. a. 0.00513 s-1 b. 0.00946 s-1 c. 0.00787 s-1 d. 0.0224 s-1 e. 0.000640 s-1 b or c
*February 24, 2012*

**chemistry**

For a one step reaction, the activation energy for the forward reaction is 40.0 kJ/mol and the enthalpy of reaction is -20.0 kJ /mol. Which statement below is true? a. The activation energy of the forward reaction would be affected to a greater extent than the activation ...
*February 24, 2012*

**chemistry**

A particular reaction has an activation energy of 51.6 kJ/mol-rxn. How much faster is the reaction at 50 degrees C versus 25 degrees C? a. 2 times b. 5 times c. 3 times d. half as fast d. 20% as fast help
*February 24, 2012*

**Math/Calculus.**

Suppose (x^2)*(e^(-2y))= ln(xy) Find dy/dx by implicit differentiation.
*February 22, 2012*

**chemistry**

how does the electrolyte paste in a battery work
*February 22, 2012*

**math**

I have a rectangle w/ 20 boxes in it what would 1/5 of the boxes be?
*February 22, 2012*

**calculus**

The voltage signal from a standard European wall socket can be described by the equation V(t)=325sin100 pi x , where t is time, in seconds and V is the voltage at time, t. determine the period frequency and amplitude
*February 21, 2012*

**English**

Tree
*February 21, 2012*

**physics/chemistry**

so it is a physics project
*February 21, 2012*

**physics/chemistry**

if i'm testing conductivity of different salts?
*February 21, 2012*