Friday

May 27, 2016
Total # Posts: 516

**Chemistry**

Which of the following is(are) true for an exothermic reaction? [H = enthalpy] A) ƒ´H¢X > 0 B) ƒ´H¢X < 0 C) Hreactants > Hproducts D) Hreactants < Hproducts E) Hreactants = ƒ´H¢X The square means delta.
*January 30, 2011*

**English**

Thanks everyone i Got a 100% also!!! :) REAL ANSWERS ARE 1)c 2)a 3)c 4)a 5)a 6)c 7)d 8)d 9)a 10)c 11)a 12)a 13)c 14)c 15)d 16)d 17)c
*January 28, 2011*

**math**

what number gives the same result when multiplied by 6 as it does when 6 is added to it?
*January 25, 2011*

**Math**

The length of a rectangle is twice its width if the area of the rectangle is 200 m squared, find its perimeter.
*January 17, 2011*

**Physics**

100 m from a traffic light, a motorist sees it to red. If he needs to accelerate at -1 m.s ^2 to stop at the traffic light, what is the initial speed, and how long did he take to stop?
*January 13, 2011*

**Chemistry**

C=3 ;H=2 and Cl=1. Therefore the empirical formula of the compound is C3H2Cl The others don't seem clear to me
*January 10, 2011*

**Chemistry**

1) C=3 ;H=2 and Cl=1 so the empirical formula of the compound is C3H2Cl. I seem not to get the others clear.
*January 10, 2011*

**Physics**

A man using a 70 kg garden roller on a level surface exerts a force 20 kgf at 45 degrees to the ground . Find the vertical force of the roller on the ground if he ; a) pulls the roller. b) pushes the roller.
*January 10, 2011*

**Algebra-please check**

Thank you
*January 7, 2011*

**Algebra-please check**

Could someone please check my solution-Thank you-DRWLS helped me set it up and I solved it, I think From the top of a mountain 150 feet high, Jessie stands at the safety rail on the edge and looks below. The angle of elevation from his bike on the ground to Jessie is 38 ...
*January 7, 2011*

**Algebra II-please check**

sin 38 = .6157 .6157 = 150/x 150/.6157 = 243.6
*January 7, 2011*

**Algebra II**

From the top of a mountain 150 feet high, Jessie stands at the safety rail on the edge and looks below. The angle of elevation from his bike on the ground to Jessie is 38 degrees, how far is Jessie from his bike.Please help me to set this up Thank you
*January 7, 2011*

**Physics**

2 forces acting at a point make angles of 25 and 65 degrees respectively with their resultant which has a magnitude of 150 N .Find the magnitude of the two components.
*December 31, 2010*

**physics**

3 stings are attached on a ring. 2 of the strings make 70 degrees angle and each is pulled with 7.0 N . What force must be applied to keep the 3rd string to keep stationary?
*December 30, 2010*

**calculus**

At the instant when the radius of a cone is 3 inches, the volume of the cone is increasing at the rate of 28.27433388 cubic inches per minute. If the height is always 3 times the radius, find the rate of change of the radius at that instant?
*December 30, 2010*

**calculus**

find the inverse: y= ln (x/(x-1))
*December 27, 2010*

**Physics**

Given the info provided, this is a simple Q=mc(delta)T question. Simply plug and chug. m=10kg c=specific heat = 900j/kgxC (delta)T= 5 C The answer should be 4.5x10^4 J
*December 19, 2010*

**calculus**

the tangent line to the curve y=1/3(x^3)-3x^2+11x+15 is parallel to the line 9x-3y=2 at two points on the curve.Find the two points.
*December 13, 2010*

**Precalculus**

Doing some test corrections and not seeing this....Please help: Verify. csc^4x - cot^4x = 2csc^2x-1
*December 9, 2010*

**spanish**

Do you mean a la uno voy a la clase ciencias? If so, it means "at one o'clock I go to science class."
*December 9, 2010*

**Precalculus**

Having trouble with this: Verify: csc^4x-cot^4x=2csc^2x-1 *the numbers after the carets are to the power of
*December 9, 2010*

**Chemistry**

When a 1.350g sample of element X is heated in a stream of chlorine gas 6.67g of XCl3 are formed.1.) What(write) is a balance equation for the reaction using 'X' for the element? 2.) Calculate the atomic weight of X. 3.)What mass of X is left unreacted? 4.)When 1.00 ...
*December 9, 2010*

**Chemistry**

When a 1.350g sample of element X is heated in a stream of chlorine gas 6.67g of XCl3 are formed.1.) What(write) is a balance equation for the reaction using 'X' for the element? 2.) Calculate the atomic weight of X. 3.)What mass of X is left unreacted? 4.)When 1.00 ...
*December 9, 2010*

**physics**

Two identical containers are open at the top and are connected at the bottom via a tube of negligible volume and a valve which is closed. Both containers are filled initially to the same height of 1.00 m, one with water, the other with mercury, as the drawing indicates. The ...
*December 4, 2010*

**Statistics**

A student studies for a statistics exam where all questions are true or false. A reputable source indicates that with studying the student has a 90% chance of answering each question correctly. There are only three questions on the test. What is the probability that the ...
*November 28, 2010*

**physics help **

ye i dont understand ho your explaining with the other guy who posted it. i dont know where you get any of your number from
*November 8, 2010*

**Physics help please**

The drawing shows a collision between two pucks on an air-hockey table. Puck A has a mass of 0.030 kg and is moving along the x axis with a velocity of +5.5 m/s. It makes a collision with puck B, which has a mass of 0.055 kg and is initially at rest. The collision is not head-...
*November 7, 2010*

**Physics please help cant figure this out**

im just not sure what formula exactly to use to solve each part a,b, and c
*November 5, 2010*

**Physics please help cant figure this out**

starting with an initial speed of 5.00 m/s at a height of 0.265 m, a 1.75 kg ball swings downward and strikes a 4.45 kg ball that is at rest, as the drawing shows. (a) Using the principle of conservation of mechanical energy, find the speed of the 1.75 kg ball just before ...
*November 5, 2010*

**physics please help**

for part a i got change in momentum right which was 1.8 then when i divided that by 4.05E-3 i got 4.44E-4 and it was marked wrong
*November 5, 2010*

**problem solving**

if a circuit has a 3.9k resistor and a 5/f capacitor find the current flow in the circuit at 0.005 seconds,if the maximum current flow in thecircuit is 1.5ma
*November 1, 2010*

**Science**

The normal boiling point for acetone is 56.5 Celsius. The atmospheric pressure is 630torr. What would be the boiling point of acetone, delta Hvap = 32.0 KJ/mol. What would be the vapor pressure of acetone at 25.0 Celsius. Please help me with this problem. Thank you
*October 31, 2010*

**Science**

BP -164°C ΔHvap 8.136 kJ/mol sg 2.205 J/g°C MP -182°C ΔHfus 0.928 kJ/mol sl 2.41 J/g°C Using the data above for methane, CH4, calculate the heat needed to convert 150. g of liquid methane at -175°C to a gas at 25°C.
*October 28, 2010*

**Science**

which of the following are predicted by the molecular orbital model to be stable diatomic species N22-, O22-, F22-
*October 23, 2010*

**Physics**

In a two-dimensional tug-of-war, Alex, Betty, and Charles pull horizontally on an automobile tire at the angles shown in the overhead view of the figure. The tire remains stationary in spite of the three pulls. Alex pulls with force of magnitude 226 N, and Charles pulls with ...
*October 8, 2010*

**Physics**

A 400 kg rocket sled can be accelerated at a constant rate from rest to 1600 km/h in 2.0 s. What is the magnitude of the required net force?
*October 8, 2010*

**science**

In defining the sizes of orbitals, why must we use an arbitrary value, such as 90 percent of the probability of finding an electron in that region?
*October 3, 2010*

**Science**

If you drive 20 laps around a circular race track at 100 m/s what do you know about your speed, velocity and acceleration?
*September 28, 2010*

**CHEMISTRY**

The first-order reaction, SO2Cl2 ¨ SO2 + Cl2, has a rate constant equal to 2.20 ~ 10-5 s-1 at 593 K. What percentage of the initial amount of SO2Cl2 will remain after 6.00 hours?
*September 27, 2010*

**chemistry**

The first-order reaction, SO2Cl2 ¨ SO2 + Cl2, has a rate constant equal to 2.20 ~ 10-5 s-1 at 593 K. What percentage of the initial amount of SO2Cl2 will remain after 6.00 hours?
*September 27, 2010*

**chemistry**

decomposition of H2O2 to water and O2
*September 26, 2010*

**chemistry**

why is temperature of H2O2 measured in the graduated cylinder?
*September 26, 2010*

**Math**

Simplify please...thnks X/50=(312-X)60
*September 23, 2010*

**Math Word Problem**

The question is poorly worded. But that is the way I got the answer.
*September 12, 2010*

**science**

Balancing redox reactions Balance in acid solution 1. PH3+ I2 -> H3PO4 + I- 2. ClO3- + Cl- -> Cl2 Balance in basic solution Se -> Se2- + SeO3^2- BrO- + Cr(OH)4^- -> Br- + CrO4^2-
*September 7, 2010*

**science**

I need help with balancing redox reactions Balance in acid solution: 1) PH3+ I2 --> H3PO4+ I- 2) ClO3- + Cl- --> Cl2
*September 7, 2010*

**phys**

“There are many social and cultural contexts you interact with that strongly influence development. These contexts include people you interact with daily, neighborhood factors, and larger scale social and cultural variables. In order to fully understand how the ...
*September 7, 2010*

**science**

Balance in acid solution PH3+ I2-> H3PO4+ I-
*September 6, 2010*

**chemistry**

write the net ionic equation for the following : 2CuCl(aq)-> CuCl2(aq)+ Cu(s) 4NaCl(aq)+2H2SO4(aq)+MnO2(s)-> 2Na2SO4(aq)+2H2O(l)+Cl2(g) 3KOH(aq)+Fe(NO3)3(aq)->Fe(OH)3(s)+ 3KNO3(aq)
*September 6, 2010*

**Science**

ok, i got them. just want to make sure the answer are correct. thanks
*August 20, 2010*

**Science**

Give the conjugate acid of the following bases: a) NH2-, b) CO3 ^2-, c) HS-, d) OH-
*August 20, 2010*

**Science**

Is it O2(S) is denser right? Because it's solid
*August 20, 2010*

**Science**

thanks, i typed it wrong
*August 20, 2010*

**Science**

The normal melting and boiling point of O2 are -218C and 49.8atm. a)Sketch the phase diagram for O2. b) Which is denser, O2(S) or O2 (l)? explain.
*August 20, 2010*

**science**

Could I use STP( 760 torr and 273K) to plug in the equation ?
*August 13, 2010*

**science**

The equation require 2 pressure but there is only 1 in this problem
*August 13, 2010*

**science**

On top of one of the peaks in Rocky Mountain National Park the pressure of the atmosphere is 500.torr. Determine the boiling point of water at this location. The heat of vaporization of water is 40.7 kJ/mol? Show work for me please! Thank you
*August 13, 2010*

**science**

which would have a lower melting point, C3H6 or CH30H? explain please!
*August 12, 2010*

**science**

NH2-,NH3, and NH4+ have H-N-H bond angles of 105, 107, and 109. Explain this variation in bond angles
*August 12, 2010*

**science**

NH2-, NH3, and NH4+ have H-N-H bond angles of 105, 107 and 109. Explain this variation in bond angles.
*August 10, 2010*

**science**

which would have a lower melting point, C3H6 or CH30H? explain.
*August 10, 2010*

**Science**

Consider the following reaction: 2Na + Cl2 2NaCl ΔH = -821.8 kJ (a) Is the reaction exothermic or endothermic? (b) Calculate the amount of heat transferred when 5.6 g of Na reacts at constant pressure. (c) How many grams of NaCl are produced during an enthalpy ...
*August 3, 2010*

**chemistry**

I don't get which one is Tfinal, and Tinitial for both of them can you explain it? thank you
*August 3, 2010*

**chemistry**

A small “coffee cup” calorimeter contains 110. g of H2O at 22.0°C. A 100. g sample of lead is heated to 90.0°C and then placed in the water. The contents of the calorimeter come to a temperature of 23.9°C What is the specific heat of lead?
*August 3, 2010*

**Chemistry**

A gaseous mixture of O2, H2, and N2 has a total pressure of 1.50 atm and contains 8.20 g of each gas. Find the partial pressure of each gas in the mixture They don't give you Volume and Temperature. Please explain it to me, thank you!
*August 2, 2010*

**chemistry**

Sterling silver, an alloy of silver and copper, contains 7.5 percent copper by mass and has a density of 10.3 g/cm3. How many copper atoms are in a sterling silver sphere whose radius is 2.0 in?
*August 2, 2010*

**chemistry**

Calculate the molarity of the solution produced by mixing (a) 50.0 ml of 0.200 M NaCl and 100.0 ml of 0.100 M NaCl;
*July 27, 2010*

**Math**

cool
*May 10, 2010*

**math**

what is 15% of 35?
*April 28, 2010*

**english**

write a pargraph of about 50 words on the topic job seeking is a task that needs courage as well as patience
*April 22, 2010*

**chemistry**

find the mass of solute needed. 3.0 liters of 2.0 M NaOH. or 500ml of 1.5 M NaCl?
*April 20, 2010*

**Grade 12 English - College Assignment**

job seeking and courage
*April 8, 2010*

**12th grade**

cos x sin x
*March 31, 2010*

**stats**

A statistics practitioner formulated the following hypothesis: H0 : ì = 200 against H1 : ì < 200 and learned that x = 190 n = 9 and ó = 50. The p– value of the test is (1) 0.6 (2) 0.2743 (3) 0.7743 (4) −0.2743 (5) Cannot be found with ...
*March 31, 2010*

**stats**

A bakery stated that the average number of breads sold daily is 3000. An employee thinks that the actual value might differ from this and wants to test this statement. The correct hypotheses are: (I think it is 1) (1) H0 : ¦Ì = 3000 H1 : ¦Ì not= ...
*March 31, 2010*

**stats**

A statistics practitioner wishes to test the following hypothesis: H0 : ì = 600 against H1 : ì < 600 A sample of 50 observations yielded the statistics: mean x = 585 and standard deviation sx = 45. The test statistic of a test to determine whether there is ...
*March 31, 2010*

**3rd grade**

ciopanam
*March 23, 2010*

**calculus**

D) would actually be approximately 9.23 seconds. 1362/16=85.125
*March 21, 2010*

**Math209**

Selling shirts. If a vendor charges p dollars each forrugby shirts, then he expects to sell 2000 - 100p shirts ata tournament. a) Find a polynomial R(p) that represents the total revenuewhen the shirts are p dollars each. b) Find R(5), R(10), and R(20). c) Use a bar graph to ...
*March 13, 2010*

**maths**

The plane is flying at an altitude of 8 miles and is 175 miles from the runway, as measured from the ground. What angle will the plane's path make with the runway? Round your answer to the nearest hundredth.
*March 12, 2010*

**Physics**

Hi, I have the following question: 1. The index of refraction for a prism is given by the equation: n = 1.58 − (6.41 x 10^4)λ where λ is the wavelength in meters. Light is incident at 28°. Find the exit angle ß for light of a) 800 nm b) 633 nm c) 540 ...
*March 7, 2010*

**accounting**

What is the Journal Entry for: Sold goods to Smithsons for $700 that costs $300. Terms of n/30 were offered. As a courtesy to Smithsons, $125 of frieght was added to the invoice for which cash was paid directly to the UPS by Opals, INC? Need This answer ASAP!
*February 27, 2010*

**Physics**

The typical resistance of the tungsten filament of a 60 watt incandescent light bulb when it is turned off is 24 ohms and its resistance when operating from a 120 volt power source is 240 ohms. Generally, an incandescent light bulb filament is most likely to “burn out&#...
*February 23, 2010*

**Math 116 algebra **

plug in the x values in the equation to find the y values.
*February 23, 2010*

**Physics**

No, this is all of the information that is provided.
*February 23, 2010*

**Physics**

The nominal resistance R of the resistor used in this experiment was printed on the resistor by the manufacturer. According to the manufacturer, the actual resistance of the resistor should not differ from its nominal value by more than 1%. Does your most accurate measured ...
*February 23, 2010*

**Physics**

This is the question that was provided, no more information.
*February 23, 2010*

**math**

use a calculator!
*February 23, 2010*

**chem**

Benzaldehyde, C6H5CHO}, has a normal boiling point of 179.0 C and a critical point at 422 C and 45.9 atm. Using a phase diagram, estimate its vapor pressure at 125 Degrees (I'm putting this back up again. Since I still didn't understand it but the answer to it was 171 ...
*February 15, 2010*

**chem**

Heat of vap. is 38.9 KJ/mol
*February 15, 2010*

**chem**

How much heat is required to raise the temperature of 200 g CH3OH from 20 to 30 degrees and then vaporize it at 30 degrees. The molar heat capacity of CH3OH is 81.1 J/Mol/K. Okay...the answer is approximately around 254. It was a homework problem. The question is how do you ...
*February 15, 2010*

**Chemistry**

thank you very much. my chemistry is very rusty so i need a refresher.
*February 15, 2010*

**Chemistry**

1.) A vapor volume of 1.17 L forms when a sample of liquid CH3CN absorbs 1.00 KJ of heat at its normal boiling point (81.1 C and 1 atm). What is the heat of vaporization in KJ per moles of CH3CN? 2.) The vapor pressure of water at 25 C is 23.76 torr. If a 1.25 g sample of H20 ...
*February 15, 2010*

**chemistry**

How much heat is required to raise the temperature of 200 g CH3OH from 20 to 30 degrees and then vaporize it at 30 degrees. The molar heat capacity of CH3OH is 81.1 J/Mol/K. Okay...the answer is approximately around 254. It was a homework problem. The question is how do you ...
*February 13, 2010*

**chemistry**

Btw what do I do about the molar heat capacity
*February 13, 2010*

**chemistry**

hm...I dont remember posting this problem but thank you again dr.bob, I can definetly always count on you
*February 13, 2010*

**chemistry**

How much heat is required to raise the temperature of 200 g CH3OH from 20 to 30 degrees and then vaporize it at 30 degrees. The molar heat capacity of CH3OH is 81.1 J/Mol/K. Okay...the answer is approximately around 254. It was a homework problem. The question is how do you ...
*February 13, 2010*

**chem**

The normal melting point of copper is 1357 K and heat of fusion of Cu is 13.05 KJ. How much heat, in kilojoules, is evolved when a 3.70 kg sample of of molten Cu freezes?
*February 11, 2010*

**Chem.**

nevermind i had it right the whole time. thank you
*February 10, 2010*

**Chem.**

Benzene has a heat of vaporization of 30.72 kj/mol and a normal boiling point of 80.1 degrees celcius. At what temperature does Benzene boil when the external pressure is 440 torr? Since...I didn't get the right answer. I'll just show my work and see if anyone can help...
*February 10, 2010*