Tuesday

September 23, 2014

September 23, 2014

Number of results: 18,520

**chemistry**

Which of the following equations represents a reaction for which the delta H can be called a standard enthalpy of formation, delta Hf? a) FeO(s) + CO2(g) -> FeCO3(s) b) 1/2 N2(g) + 2 O(g) -> NO2(g) c) 2 Na(s) + Cl2(g) -> 2 NaCl(s) d) Ba(s) + N2(g) + 3 O2(g) -> Ba(...
*January 23, 2012 by timmy*

**Chemistry**

Given the following hypothetical equations, 2A + B → 3C + 2D ΔH = -46.7kJ C → B ΔH = 13.1kJ 2E → B ΔH = 84.5kJ, what is the enthalpy change (kJ) for the following reaction? A → D + 2E
*March 7, 2012 by John*

**chemistry**

A. Strong Base 1.) What is the concentration of a solution of KOH for which the pH is 11.89? 2.) What is the pH of a 0.011M solution of Ca(OH)2? B. Weak Acid 1.) The pH of a 0.060M weak monoprotic acid HA is 3.44. Calculate the Ka of the acid. 2.) The pH of 0.100M solution of ...
*January 20, 2011 by jaycab*

**Chemistry **

Why wouldn't you do this reaction directly in a lab (and would rather use Hess' Law to determine the enthalpy of formation)?: 1/2N2(g) + 2H2(g)+ 1/2Cl2(g) -> NH4Cl(s) I don't think the reactants are that dangerous...? It's still pretty safe to do in a lab, isn't it? Are ...
*February 18, 2013 by a Canadian*

**Physics**

A stone that starts at rest is in free fall for 8.0 s. a.Calculate the stone's velocity after 8.0 s. b. What is the stone's displacement during this time? Given: t = 8.0 s a = 9.81 m/s^2 For a, in order to calculate the velocity, should i use d = vit + 1/2 at^2 and only use ...
*December 25, 2009 by Priscilla*

**chemistry**

the enthalpy of fusion of ice is 6.02 kJ/mol. the heat capacity of liquid water is 75.4 J/molC. What is the smallest number of ice cubes at 0 degrees C each containing one mole of water, necessary to cool 500g of liquid water initially at 20.0 degree C to 0.0 degree C
*May 24, 2011 by el*

**Maths**

The distance from TDC (top dead centre) for the pin is given by x when the crank is at angle . Hence : i) Give an equation for x in terms of the other variables (r, L and ). ii) If the crank rod is rotating at a constant value of ω calculate the speed of ...
*May 17, 2011 by Karl Haxell*

**math**

The distance from TDC (top dead centre) for the pin is given by x when the crank is at angle . Hence : i) Give an equation for x in terms of the other variables (r, L and ). ii) If the crank rod is rotating at a constant value of ω calculate the speed of ...
*May 17, 2011 by Karl Haxell*

**chemistry**

1998 scientists using a special type of electron microscope were able to measure the force needed to break a single chemical bond. If 2.0 x 10^-9 N was needed to break a C-Si bond, estimate the bond enthalpy in kJ/mol. Assume that the bond had to be stretched by a distance of ...
*September 26, 2011 by Amber*

**Maths**

In an orthonormal system, you're given the following: Point P(1,2) Lina a=cartesian eqn:4x-3y+6=0 Line b=parametric eqns:x=-5+3& y=-& (real n°) Circle z=cartesian eqn:x²+y²-2x-3=0 (a)Calculate the angle between lines a an b (b)Calculate the coordinates of the point of ...
*May 4, 2008 by Anonymous*

**Mathematics**

In an orthonormal system, you're given the following: Point P(1,2) Lina a=cartesian eqn:4x-3y+6=0 Line b=parametric eqns:x=-5+3& y=-& (real n°) Circle z=cartesian eqn:x²+y²-2x-3=0 (a)Calculate the angle between lines a an b (b)Calculate the coordinates of the point of ...
*May 18, 2008 by Anonymous*

**Chemistry**

What is the enthalpy change (in kJ) for burning 49.0 g of methyl alcohol? I tried this question and got the wrong answer of 1047.74. A gas is compressed from 73.7 L to 1.9 L at 0.70 atmospheres? In addition a total of 4400 J of heat are gained from warmer surroundings. What is...
*October 19, 2012 by Anonymous*

**Math**

If a = 3i + 2j - k and b = -2i + j calculate each magnitude. a) a + b I got sqrt3, but the answer at the back of the book says sqrt11. 2) If D(3,4,5) and E(-2,1,5) are points in space calculate each expression and state what it represents. |OD| can you please do those and ...
*March 29, 2008 by Anonymous*

**college chemistry**

Use the thermochemical equations shown below to determine the enthalpy (kJ) for the reaction: H2SO3(l)=>H2S(g) + 3/2O2(g) H2SO3(l)=>H2O(l) +SO2(g) DH=62KJ SO2(g)=>S(s) + O2(g) DH=297KJ H2S(g) + 1/2O2(g)=>S(s) + H2O(l) DH=-155KJ
*October 24, 2010 by sara*

**Chemistry**

A 5.0-g Sample of KBr at 25.0 degrees celsius dissolves in 25.0 degrees celsius 25.0 mL of water also at 25.0 degrees celsius. The final equilibrium temperature of the resulting soltution is 18.1 degrees celsius. What is the enthalpy of of solution in kilojoules per mole of KBr?
*December 2, 2010 by Sally*

**Chemistry**

The enthalpy of vaporization of chloroform (CHCl3) is 29.2 kJ mol-1 at its normal boiling point 61.2 Celsius. what is the standard change in entropy for vaporization of chloroform at its normal boiling point? Answer I got was 29.2/334.2 = 0.0873. (CORRECT?)
*April 2, 2013 by Viv*

**chemistry**

how in the world do you do this problem? Use the thermochemical equations shown below to determine the enthalpy (kJ) for the reaction: H2SO3(l)=>H2S(g) + 3/2O2(g) H2SO3(l)=>H2O(l) +SO2(g) DH=62KJ SO2(g)=>S(s) + O2(g) DH=297KJ H2S(g) +1/2O2(g)=>S(s) + H2O(l) DH=-...
*October 24, 2010 by anonymous*

**chemistry - energy and change rev (help)**

the below 2questions i could not answer while revising for this chapter pls help me out a little. 58. When a vehicle is parked in the sunlight on a hot summer day, the temperature inside can approach 55°C. One company has patented a non-CFC propelled aerosol that can be ...
*March 23, 2011 by Babelii*

**chemistry**

For a particular isomer of C8H18, the following reaction produces 5113.3 kJ of heat per mole of C8H18(g) consumed, under standard conditions. C8H18(g) + 25/2(O2)(g) -> 8CO2(g) + 9H2O(g) DeltaH= -5113.3 kJ What is the standard enthalpy of formation of this isomer of C8H18(g)?
*January 29, 2012 by Mike*

**chemistry**

calculate [h3o] in solutions. 0.040 of HCl and 0.080 HOCl. 2. calculate OH for the solutions of 0.0063 ba (OH)2 and 0.0110 of BaCl2
*April 11, 2010 by anonymous*

**math**

Consider the function defined below. y = 2t3 - 4t2 + 3 (a) Calculate the second derivative. y '' = (b) Calculate the third derivative. y ''' =
*June 21, 2010 by Jack*

**Chemistry**

Calculate how much heat 32.0 g of water absorbs when it is heated from 26.0°C to 73.5°C. In joules, and then we have to calculate calories too, how is that done? I was absent. Thanks so much!
*May 25, 2011 by Jane*

**Chemistry **

Calculate the wavelength of broadcast waves. Calculate the energy associated with the broadcast frequency for WPHT, 1210 kHz.
*November 5, 2011 by Anonymous*

**math**

calculate the mass (in SI units) of a 150ib human being? m= Calculate the weight ( in English units) of a 200kg rhino m=
*January 26, 2012 by bree*

**Chemistry**

When 23.6 of calcium chloirde CaCl2 was dissolved in water in a calorimeter, the temperature rose from 25.0 degrees C to 21.56 degrees C. If the heat capacity of the solution and the calorimeter is 1071 J/ degrees C, what is the enthalpy change when 1 mol of sodium nitrate ...
*November 1, 2007 by Lauren*

**chemistry**

When water freezes, the phase change that occurs is exothermic (DH = -6.02 kJ). Based on the change in enthalpy, you would expect that water would always freeze. Use the concepts of entropy and free energy to explain why this phase change is favourable only below o degrees ...
*April 6, 2008 by Sarah*

**Chemistry**

For ethanol, C2H5OH, which is mixed with gasoline to make the fuel gasohol, H°f = -277.63 kJ/mol. Based upon data in Table 6.2, and that the density of ethanol is 0.787 g•cm-3, the number of kilojoules released by burning completely 2.40 gallons of ethanol is ? *Table 6.2 ...
*October 16, 2011 by A*

**epidemiology**

In a fictitious study, 100 out of 1000 people aged 60 years and over were positive in detecting breast cancer using Tumour Biopsy (gold standard). Using mammography, 90 of breast cancer patients and 135 healthy persons were also positive by this test. (I) Calculate and ...
*August 18, 2012 by Ekrem*

**ap chem**

A 9.00 M solution of a weak acid, HA, has a pH of 1.30 1.) calculate [A-] at equilibrium 2.) calculate [HA] at equilibrium Use pH to get (H^+). Ka = (H^+)(A^-)/(HA) (A^-) = (H^+). (HA) = 9 Plug and chug. Post your work if you get stuck.
*March 22, 2007 by Jaron*

**Physics**

A particle's initial velocity is given by vox = -1.0 m/s and voy = 3.0 m/s. Its acceleration is ax = 0.50 m/s^2 and ay = -0.90 m/s^2 (a) Calculate its velocity 2.0 s later. (b) Calculate its displacement at that time.
*October 4, 2009 by Sandhu*

**statistics**

GIVEN THE FOLLOWING STATISTICAL VARIABLES A:m(A)=5 B:m(B)=13 var(A)=25 Var(B)=6 1.calculate mean of Z= 4B-2A 2.Calculate the Standard Deviation assuming cov (A,B)=0
*August 17, 2010 by RASHMI*

**physics**

A force of 303.0 N is used to push a 160 kg mass 30.0 m horizontally in 3.00 s. (a) Calculate the work done on the mass. 1 kJ (b) Calculate the power developed. 2 kW
*December 12, 2011 by Anonymous*

**chemistry**

calculate r.m.s velocity of he molecule at 300k.also calculate the total k.e(in calories)of the molecules in one litre he at 300k & 1atm?
*July 6, 2012 by dip*

**Math calculate depreciation**

please explian how to calculate depreciation for federal income taxes what method do I use thanks :)
*November 14, 2007 by Anonymous*

**calculus**

calculate the indefinite integral 2sec^2x dx (cosx)/(sin^3x) dx calculate the definite integral interval pi/4, pi/12 csc2xcot2x dx
*January 6, 2008 by anonymous*

**geometry**

In the following figure given a circle C(o,3) Bp=AB and BA^N = 30 a) Calculate AP,BN and AN b)Calculate AQ and BQ c) Show That M is the mid point of (AP) d)Show that (OM)is perpendicular to (A)
*April 16, 2010 by Nour *

**physics **

A spherical conductor has a radius of 14.0 cm and charge of 26.0 µC. Calculate the electric field and the electric potential (a) r = 10.0 cm, (b) r = 20.0 cm, and (c) r = 14.0 cm from the center. how do i calculate k?
*February 7, 2012 by confused*

**Chemistry-Help**

An AM radio station broadcasts at 1060 kHz. Calculate the wavelength of the corresponding radio waves. How do I calculate this?
*April 30, 2012 by Liz*

**Chemistry**

What is the entropy of CH3OH? My CRC tables list 239.865 J/K*mol @ 298.15o K. Do you also know the enthalpy? deltaHof= -201.000 kJ/mol according to the CRC Handbook,1995-96 edition.
*March 26, 2007 by Meg*

**Physics**

An electric dipole comprised of two charges Q and -Q are separated by a distance of 3.0 cm. Assume Q = 2.0x10^-6 C and -Q = -2.0x10^-6 C. Find the magnitude and direction of the electric field vector E and point P, which is 4.0 cm to the right of the center of -Q. Find the ...
*March 13, 2012 by Michelle*

**chemistry 12**

Im doing a worksheet and i had to draw PE diagram which had the Ea(activation energy)at 80kJ and the enthalpy change is -40kJ. *All the reactants and products are gases Then it asks to describe what would happen to the diagram if the temperature dropped 25 degrees Celsius. Im ...
*December 14, 2012 by Anonymous*

**Thermodynamics**

a rigid vessel of volume 1m(^3) contains steam at 20bar and 400 degrees Celcius. The vessel is cooled until the steam is just dry saturated. Calculate the mass of steam in the vessel, the final pressure of the steam and the heat rejected during the process. The answers should ...
*March 12, 2010 by Claire*

**Please help with really hard chem question?**

An electrolysis experiment was run for 17.5 minutes at an average current of 191 milliamps (mA). The mass lost by the copper anode was 0.0679 grams. a) Calculate the number of coloumbs transferred. (coloumb=ampsxsec) b) Calculate the moles of copper lost from the anode. c) ...
*April 16, 2014 by Dianne*

**Physics**

A 275 kg piano slides 4.0 m down a 30° incline and is kept from accelerating by a man who is pushing back on it parallel to the incline. The effective coefficient of kinetic friction is 0.40. a) Calculate the magnitude of the force exerted by the man. b) Calculate the work ...
*December 11, 2013 by Josh*

**Physics**

A 275 kg piano slides 4.0 m down a 30° incline and is kept from accelerating by a man who is pushing back on it parallel to the incline. The effective coefficient of kinetic friction is 0.40. a) Calculate the magnitude of the force exerted by the man. b) Calculate the work ...
*December 11, 2013 by Josh*

**Accounting 7**

Noteworthy, Inc., produces and sells small electronic keyboards. Assume that you have the following information about Noteworthy’s costs for the most recent month. Depreciation on factory equipment $800 Depreciation on CEO's company car $100 Speakers used in the keyboard $1,...
*August 31, 2014 by Mia*

**physic**

Calculate the mass (in SI units) of a 150 lb human being. m= (correct unit) Calculate the weight (in English units of a 2000 kg rhinoceros.
*January 27, 2012 by sam*

**chemistry**

Consider the hypothetical elements X and Y. Suppose the enthalpy of formation for the compound XY is ƒ{336 kJ/mol, the bond energy for X2 is 414 kJ/mol, and the bond energy for Y2 is 159 kJ/mol. Estimate the XY bond energy in units of kJ/mol.
*December 13, 2010 by chemistry*

**chemistry**

Consider the hypothetical elements X and Y. Suppose the enthalpy of formation for the compound XY is -336 kJ/mol, the bond energy for X2 is 414 kJ/mol, and the bond energy for Y2 is 159 kJ/mol. Estimate the XY bond energy in units of kJ/mol.
*December 13, 2010 by Jude*

**AP physics **

i really need help on this problem!! Three blocks are connected,on a horizontal frictionless table and pulled to the right with a force T3 = 64.4 N. Assume that m1 = 12.5 kg, m2 = 25.0 kg, and m3 = 31.7 kg. (a) Calculate the acceleration of the system (b)Calculate the tensions...
*September 24, 2010 by annamaria *

**Physical Science**

How do you calculate the mass and volume of an irregular solid object and calculate the density of that object?
*January 25, 2009 by Alex*

**chemistry**

% recovery: how do i calculate it? we're doing a recrystallization in chem class we used 0.1 g and we recovered 0.3 g how do i calculate the percent recovery?
*February 9, 2011 by jessie*

**calculate ratios**

Calculate the amount of drug in a ratio solution. How many micrograms are in 1ml of a 1:5000 solution?
*March 6, 2012 by Vicki*

**Chemistry**

Please show me how to work! Ethane, C2H6(g) can be made by reaction of hydrogen gas with acetylene, C2H2(g). the standard enthalpies of formation of ethane and acetylene are -84.68 and +226.73 kJ mol-1, respectively. what is the reaction enthalpy for the production of one mole...
*October 20, 2012 by Sam*

**Chemistry(explain Please)**

How would i find the following? I just need an explanation. I'm stuck. I have many other questions like this and i need to know how to do them. The specfic heat of ice is 2.05 J/g. In a calorimeter, 10.0 g of ice melts at 0oC. The enthalpy of fusion of the ice is 334 J/g. How ...
*June 22, 2012 by anonymous*

**PHYSICS**

I don't know where to start solving this question. Please help! A 320 kg piano slides 3.7 m down a 32 degree incline and is kept from accelerating by a man who is pushing back on it parallel to the incline. The effective coefficient of kinetic friction is 0.39. Calculate the ...
*November 8, 2010 by MegP*

**Accounting 7**

coteworthy, Inc., produces and sells small electronic keyboards. Assume that you have the following information about Noteworthy’s costs for the most recent month. Depreciation on factory equipment $800 Depreciation on CEO's company car $100 Speakers used in the keyboard $1,...
*September 1, 2014 by Mia*

**Chemistry**

A reaction is peformed in which 50 ml of .400M silver nitrate and 75 ml of .100M hydrochloric acid are mixed together. The initial temperature of the solutionn was 25 C and the final temperature was 27.2 C. What is the enthalpy, in kj/mol, for the formation of the precipitate...
*November 18, 2012 by Lydia*

**chemistry**

Baking soda is sodium bicarbonate (NaHCO3). When you heat baking soda, it breaks down into sodium carbonate powder (Na2CO3), water vapor, and carbon dioxide. The enthalpy of this reaction is 129 kJ. a. Write a correct, balanced thermochemical equation for this reaction. (...
*April 16, 2014 by Anonymous*

**chemistry**

The electron in a hydrogen atom is excited and makes a transition from n=2 to n=7 a. calculate the energy of the photon absorbed in joules. b. calculate the wavelength of the photon in meters HOW DO I DO THIS?
*March 21, 2011 by Tina*

**physics**

Calculate the cost of operating a 65 W light bulb continuously for a 30-day month when electrical energy costs $0.23/kW·h. $ 1 How do you calculate cost? whats the equation?
*May 11, 2012 by Alice*

**Math (Finance)**

You have a note in the amount of $10,000 at 9.5% interest running from january 5. to april 16 a. calculate the ordinary intrest. b. calculate the exact interest.
*October 31, 2012 by Renee*

**Chemistry - Solubility**

Given: Concentration of HCl is 0.1388M 0.5 g of Ca(OH)2 was placed in a flask. 100mL of 0.05M NaOH was poured into the flask. 25mL aliquot was filtrated and used for titration. Suppose to calculate the OH^- equilibrium concentration from the titration data, as well as the OH...
*March 31, 2014 by PleaseHelpThankYou!*

**Chemistry**

The ΔHof of gaseous dimethyl ether (CH3OCH3) is –185.4 kJ/mol; the vapour pressure is 1.00 atm at –23.7oC and 0.526 atm at –37.8oC. a) Calculate ΔHovap of dimethyl ether. b) Calculate ΔHof of liquid dimethyl ether Any idead how to calculate for the heat of ...
*December 11, 2012 by xavier*

**physics**

Having trouble with this one: A capacitor having a capacitance of 10uF is charged by 100v battery. A.)Calculate the charge on the capacitor? B.)calculate the energy stored in the capacitor? C.) the terminals of the capacitor is now disconnected from the batery and the ...
*February 28, 2010 by morgan*

**Physics**

Consider the circuit shown in the figure below. Use the following as necessary: R1 = 11.00 Ù, R2 = 1.40 Ù, and V = 6.00 V. (a) Calculate the equivalent resistance of the R1 and 5.00 Ù resistors connected in parallel. 1 Ù (b) Using the result of part (a), calculate the combined...
*October 5, 2010 by chuck*

**Physics**

A rectangular coil of 70 turns, dimensions 0.100 m by 0.200 m and total resistance 10.0 ohms, rotates with angular speed 32.0 rad/s about the y axis in a region where a 1.00 T magnetic field is directed along the x axis. The rotation is initiated so that the plane of the coil ...
*July 2, 2011 by Mike*

**Chemistry**

Can someone check my answers please? I had specific trouble with 7, 13, and 27 (I'm pretty sure my other answers are correct; some reassurance would be nice though). And I have a small question about 8. 1. The ΔHf of an element in its standard state is defined to be 0 kJ/...
*March 3, 2013 by a Canadian*

**Chemistry**

Explain the significance of positive and negative values for each thermodynamic quantity in the free energy equation. (enthalpy change, entropy change, and free energy change) I think this is something you can find in your text/notes. If not, explain what you don't understand ...
*May 14, 2007 by Dave*

**Will Someone please respond! Chem**

How would i find the following? I just need an explanation. I'm stuck. I have many other questions like this and i need to know how to do them. The specfic heat of ice is 2.05 J/g. In a calorimeter, 10.0 g of ice melts at 0oC. The enthalpy of fusion of the ice is 334 J/g. How ...
*June 22, 2012 by anonymous*

**Intro Chemistry**

Which molecule based on the following enthalpies is the most stable? Molecule A: -70 kJ/mol Molecule B: 100 kJ/mol Molecule C: 145 kJ/mol Is it Molecule A? Isn't the lower the enthalpy the more stable the molecule? Thank You
*April 4, 2010 by echem*

**college chemistry**

Dry ice is solid carbon dioxide. Instead of melting, solid carbon dioxide sublimes according to the following equation: CO2(s)--> CO2(g). When dry ice is added to warm water, heat from the water causes the dry ice to sublime more quickly. The evaporating carbon dioxide ...
*November 9, 2009 by Eddie*

**statistics please help**

A student measures three lengths a, b and c in cm and a time t in seconds: a = 40 ± 5 b = 30 ± 3 c = 20 ± 1 t = 1.2 ± 0.1 What is a+b a+b+c a/t (a+c)/t Calculate (1.23 ± 0.03) + pi Question 9.4. Calculate (1.23 ± 0.03) × pi Can you do a sample calculation of each of those ...
*October 19, 2008 by Sam*

**Science**

an object 5.50 cm high is placed 100 cm from a converging lens that has a focal length of 40.0cm. a)Calculate the image distance b)Calculate the hight of the image height
*January 4, 2010 by Ramandeep *

**Chemistry**

I-I:150 F-F:160 C-C:350 H-H:435 (a) Calculate the energy of the I-F bond. Express your answer in units of kJ/mol. unanswered (b) Calculate the % ionic character of the I-F bond.
*March 5, 2013 by Anonymous*

**chemistry**

use thermochemical equations shown below to determine enthalpy for the reaction: H2CO3-->H2O+CO2 1) H2CO3 --> H2CO + O2 H; 224 KJ 2)H2CO + O2 --> H2O + CO2 H; -100KJ I know this problem is one that you have to rewrite the equations to get the equation in the original ...
*November 20, 2009 by Brittany*

**chemistry**

use thermochemical equations shown below to determine enthalpy for the reaction: H2CO3-->H2O+CO2 1) H2CO3 --> H2CO + O2 H; 224 KJ 2)H2CO + O2 --> H2O + CO2 H; -100KJ I know this problem is one that you have to rewrite the equations to get the equation in the original ...
*November 20, 2009 by Brittany*

**PHYSICS**

a. A 25 nC particle and a – 7 nC particle is interacting with each other at a certain distance. Find the force between the two charges @ 3.0 cm and 1.0 cm Calculate and draw each of the particle’s electric fields. Calculate the electric potential values of the two particles. ...
*August 18, 2011 by KAIT*

**Physics**

A long thin rod lies along the x-axis from the origin to x=L, with L= 0.890 m. The mass per unit length, λ (in kg/m) varies according to the equation λ = λ0 (1+1.410x2). The value of λ0 is 0.700 kg/m and x is in meters. 1. Calculate the total mass of the ...
*February 11, 2014 by Molly*

**Physics**

A long thin rod lies along the x-axis from the origin to x=L, with L= 0.890 m. The mass per unit length, λ (in kg/m) varies according to the equation λ = λ0 (1+1.410x2). The value of λ0 is 0.700 kg/m and x is in meters. 1. Calculate the total mass of the ...
*February 11, 2014 by Molly*

**physical chemistry**

how do i calculate a ratio of oxidised to reduced cytochrome c Fe2+ to Fe3+ given E(mV) at 25 C and pH7 as 100 and absorbance at 550nm as 1.5 E is relative to standard hydrogen electrode i dont know how im supposed to calculate it from this data
*February 17, 2010 by lucy*

**CHEMISTRY**

Mass (before reaction): test tube + HCl(aq) + stir bar + capsule 26.600 g Mass (after reaction): test tube + HCl(aq) + stir bar + capsule 25.300 g Volume of water displaced from the squirt bottle 148 mL Temperature of the CO2(g) 287.4 K Pressure (atm) 1.032 atm Using this data...
*October 22, 2012 by Karina*

**chem**

Use bond energies to estimate the enthalpy change for the following reaction C2H2 + H2-> C2H4 i figured the bonds broken are: 1 C triple bond C 1(812kj/mol) 2 C-H 2(414kj/mol) 1 H-H 1(435kj/mol) Bonds formed 1 C=C 1(590kj/mol) 4 C-H 4(435kj/mol) Is this right
*November 12, 2008 by tomi*

**chemistry**

1. Calculate the volume of carbon dioxide at 273 K and 1.01 * 10^5 Pa which would be produced when 1.25g of calcium carbonate reacts completely with HCL. and 2. When 41.18 cm^3 of a solution of silver ions with concentration of .2040 mol dm^-3 is added to a solution of XO4 -3 ...
*May 19, 2008 by ANn*

**Physics - please help!!..**

A long thin rod lies along the x-axis from the origin to x=L, with L= 0.890 m. The mass per unit length, λ (in kg/m) varies according to the equation λ = λ0 (1+1.410x2). The value of λ0 is 0.700 kg/m and x is in meters. 1. Calculate the total mass of the ...
*February 12, 2014 by Molly*

**chemistry**

Calculate the change in internal energy of the system in a process for which 100J of heat is absorbed by the system from surroundings and does 85J of work. (I want to learn the solution on how to calculate it... pls. help thank you... )
*January 23, 2011 by jaycab*

**chem help**

the primary visible emissions from mercury are 404.7 nm and 435.8 nm. Calculate the frequencies for these emissions. Calculate the energy of a single photon and of a mole of photons of light with each of these wavelengths.
*March 29, 2012 by danielle*

**Chemistry **

Calculate the energy released when an electron is added to a hydrogen nucleus. Assume the transition is n= infinite to n=1. I know equation to use but how do I calculate when n is infinite and no number ?? Please some help
*November 29, 2012 by Anonymous*

**Chemistry **

How would I calculate this? I have the answer because its from a previous test I just want to know how I would calculate it. How many grams of NaCI are contained in 350. mL of a 0.133 M solution of sodium chloride?
*June 30, 2013 by Mary *

**HEALTH**

The key to using a pedometer to meet the Physical Activity Guidelines for Americans is to _________. A. First set a time goal and then calculate how rigorous the steps need to be each day to reach your goal B. First calculate how many steps are needed weekly and then match it ...
*April 17, 2013 by CARRIE*

**Chemistry**

Gasoline is primarily a mixture of hydrocarbons and is sold with an octane rating that is based on a comparison with the combustion properties of isooctane. Gasoline usually contains an isomer of isooctane called tetramethylbutane (C8H18), which has an enthalpy of vaporization...
*July 9, 2013 by Kelly*

**Chemistry**

The molar enthalpies of combustion of CH3COCOOH(l)CH3COOH(l) and CO(g) are respectively -1275kJ/mol, -875kJ/mol, and -283kJ/mol. What is the enthalpy change for the reaction below? CH3COCOOH= CH3COOH +CO a)1867kJ b)-1867kJ c)117kJ d)-117kJ e)-2433kJ I think it's d)
*July 24, 2010 by Bob*

**college chemistry**

How much heat is needed to convert 2.00 kg of liquid ammonia at -40.0 oC to its vapor at -11.0 oC? The specific heat of liquid ammonia, NH3 (l), is 4.70 J/g-K and that of the vapor NH3 (g), is 2.20 J/g-K. The enthalpy of vaporization of ammonia is 23.3 kJ/mol and its boiling ...
*May 25, 2010 by pamela*

**Physics**

A car of mass 1200kg starts from rest, accelerates uniformly to a speed of 4.0 meters per second in 2.0 seconds and continues moving at this constant speed in a horizontal straight line for an additional 10 seconds. the brakes are then applied and the car is brought to rest in...
*December 4, 2012 by Ken*

**Chemistry**

Substance A has a normal fusion point of -10 degrees C, an enthalpy of fusion = 150 Jg^-1; specific heats for the solid and the liquid are 3 and 6.2 Jg^-1C^-1 respectively. To change 150 grams of A from a solid at -40 degrees C to a liquid at 70 degrees C will require how many...
*February 1, 2009 by Amanda*

**physics**

A block of unknown mass is attached to a spring with a spring constant of 6.00 N/m and undergoes simple harmonic motion with an amplitude of 12.0 cm. When the block is halfway between its equilibrium position and the end point, its speed is measured to be 33.0 cm/s a)Calculate...
*April 27, 2009 by Jessi*

**physical chemistry PLEASE HELP!!!**

how do i calculate a ratio of oxidised to reduced cytochrome c Fe2+ to Fe3+ given E(mV) at 25 C and pH7 as 100 and absorbance at 550nm as 1.5 E is relative to standard hydrogen electrode i dont know how im supposed to calculate it from this data
*February 17, 2010 by lucy*

**Chemistry**

Magnesium fluoride dissolves in water to the extent of 8.0 10-2 g/L at 25°C. Calculate the solubility of MgF2(s) in moles per liter, and calculate Ksp for MgF2 at 25°C. I've been doing this and getting .086. Please help!
*May 26, 2010 by Kate*

**physics**

really stuck, a 90 kg skier has 140 KJ of total mechanical energy when he is at a height of 120m above the bottom of the hill. calculate the skiers kinetic energy. calculate his speed?
*October 16, 2010 by dave*

**physics**

really stuck, a 90 kg skier has 140 KJ of total mechanical energy when he is at a height of 120m above the bottom of the hill. calculate the skiers kinetic energy. calculate his speed?
*October 18, 2010 by mitch*

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