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December 19, 2014

Posts by Hannah


Total # Posts: 2,923

Chemistry
How many grams of water are needed to dissolve 27.8g of NH4NO3 (80.0 g/mol) in order to prepare a 0.452 m (molal) solution? 27.8g / 80g/mol X 0.452 = 0.157 Is this correct?
February 12, 2012

Chemistry
would it be delta T = -5.07C/m * 0.210m?
February 12, 2012

Chemistry
1) Benzene freezes at 5.45 degrees celsius. The Kf for benzene is -5.07C/m. What would be the freezing point of a 0.210m solution of octane in benzene? I am not sure how to start this. I know the equation for freezing point is Kfp * m solute.
February 12, 2012

Chemistry
so 0.30m BaCl2 has the largest delta T at 0.90 so it has the lowest freezing point. Would you agree?
February 12, 2012

Chemistry
Ok thank you!
February 12, 2012

Chemistry
so NH4NO3 is 2 and MgS04 is 4?
February 12, 2012

Chemistry
If all ionic substances completely ionized, the aqueous solution with the lowest freezing point would be 1)0.25m NH4NO3 2)0.30m BaCl2 3) 0.35m LiBr 4) 0.50m Sucrose 5) 0.40m MgSO4 I know that i have to multiply m and i to find the largest delta T. I am just not sure if the ...
February 12, 2012

Chemistry
Which of the following contributes to the bubbling from a cold can of soda when left standing at room temperature. Choose all that apply. 1) the initial rush of CO2 out of the can drags other CO2 molecules out of the solution. 2) the decrease in CO2 partial pressure lowers the...
February 12, 2012

Chemistry
Thank you for all your help!!
February 12, 2012

Chemistry
Which aqueous solution below is expected to have the lowest freezing point? Assume 100% dissociation for ionic species. 1)0.25m MgBr2 2)0.30m Na2SO4 3) 0.50m KCl 4) 1.0m sucrose 5) 0.40m Cr(NO3)3 I think that the answer is 0.30NaSO4 but I am not positive. Is this correct? ...
February 12, 2012

Chemistry(Please check)
1) The molecular mass of a substance was determined by the freezing point depression technique. The minimum data required for the determination are: a) delta T and Kf only b) delta T, Kf, and mass of solute c) delta T, Kf, mass of solute, and mass of solvent d) delta T, Kf, ...
February 11, 2012

Physics
A 520 Hz tuning fork produces a standing wave in a column of air in a closed tube. If the speed of sound is 340 m/s, what is the length of the air column?
February 11, 2012

physics
a) What is the frequency of a photon of UV radiation ( = 2.00 x 10^-7 m)? (b) Calculate the energy of a photon of UV radiation. (C) What is the frequency of a photon of infrared radiation ( = 1.083 x 10^-6 m)? (d) Calculate the energy of a photon of infrared radiation. (e) How...
February 11, 2012

Physics
In black-and-white photography, a photon energy of about 4.00 x 10-19 J is needed to bring about the changes in the silver compounds used in the film. (a) What is the frequency of the light needed to bring about these changes? (b) Explain why a red light used in a darkroom ...
February 11, 2012

Chemistry
when 7.50 grams of iodine (I2) is added to 48.7grams of carbon tetrachloride (CCl4), the iodine dissolves and a solution is formed. The weight percent of the iodine in the solution is? 7.50g I2/ 7.50 + 48.7 X 100 = 13.3 Did I do this correctly?
February 11, 2012

Chemistry(Please check)
Ok now I got 0.0931, so this is the mole fraction for NaCl?
February 10, 2012

Chemistry(Please check)
Ok so 100/58.44= 1.71
February 10, 2012

Chemistry(Please check)
1) If exactly 100.0 grams of NaCl (mm=58.44g/mol) are dissolved in 300 grams of water (mm=18.02g/mol), the mole fraction of NaCl is? a) 1.71 b) 0.0932 c) 0.250 d) 0.103 e) 4.75 I did 100g / 100g + 300g = 100/40 = 0.250. Did I do this correctly?
February 10, 2012

Chemistry(Please check)
1) The molecular mass of a substance was determined by the freezing point depression technique. The minimum data required for the determination are: a) delta T and Kf only b) delta T, Kf, and mass of solute c) delta T, Kf, mass of solute, and mass of solvent d) delta T, Kf, ...
February 10, 2012

Chemistry(Please check)
Thank you!
February 10, 2012

Chemistry(Please check)
1)For electrolyte solutions, the _____ the concentration of the electrolyte and the ____ the ion charges, then the ____ the ion-pairing. a) lower, smaller, greater b) higher, smaller, smaller c) higher, greater, greater d) lower, greater, smaller e) lower, greater, greater I ...
February 10, 2012

chemistry(Please check)
ok thank you
February 10, 2012

chemistry(Please check)
1) In comparing the phase diagram for water with that of a solution of sugar in water, all of the following decrease except a) the vapor pressure b) the boiling point c) the freezing point d) the triple point I chose the boiling point as the answer. Is this correct? Thank you.
February 10, 2012

Chemistry
Ok so then I just have to find the mass of each solution so KCl = 74.55 X 2 MgBr2 = 184.11 X 3 Na2SO4 = 94.05 X 3 Cr(SO4)3 = 340.21 X 4 So Cr(SO4)3 would have the largest delta T, so the lowest freezing point. Is this correct?
February 10, 2012

Chemistry
I understand everything except the van't Hoff factor part. I do not understand how you figure that out.
February 10, 2012

Chemistry
Which aqueous solution below is expected to have the lowest freezing point? Assume 100% dissociation for ionic species. 1)0.25m MgBr2 2)0.30m Na2SO4 3) 0.50m KCl 4) 1.0m sucrose 5) 0.40m Cr(NO3)3 I think that the answer is 0.30NaSO4 but I am not positive. Is this correct?
February 10, 2012

Chemistry
The following information is given for ether, C2H5OC2H5, at 1atm: boiling point = 34.6oC Hvap(34.6oC) = 26.5 kJ/mol melting point = -116oC Hfus(-116oC) = 7.27 kJ/mol specific heat liquid = 2.32 J/goC At a pressure of 1 atm, what is H in kJ for the process of condensing a 33.7 ...
February 9, 2012

Physics
15 At a particular location and time, sunlight is measured on a 1 m2 solar collector with an intensity of 500.0 W. If the peak intensity of this sunlight has a wavelength of 5.60 x 10-7 m, (a) What is the frequency of this light? When you input large numbers such as those in ...
February 9, 2012

Physics
What is the frequency of the electromagnetic radiation from outer space that reaches the earth with a wavelength of 1 x 105 m, and a velocity of 1 x 105 m/s?
February 9, 2012

physics
Calculate the distance traveled in 6.00 s as a given sound moves through (a) water at 25.0ºC in m/s; (b) water at 25.0ºC in ft/s; (c) seawater at 25ºC in m/s; and (d) seawater at 25ºC in ft/s.
February 9, 2012

Physics
The lower frequency limit for human hearing is usually considered to be 20.0 Hz. (a) What is the speed of sound in m/s if the air temperature is 20.0ºC? (b) What is the corresponding wavelength for this frequency?
February 9, 2012

physics
A glass bottle of soda is sealed with a screw cap. The absolute pressure of the carbon dioxide inside the bottle is 1.50 x 105 Pa. Assuming that the top and bottom surfaces of the cap each have an area of 4.20 x 10-4 m2, obtain the magnitude of the force that the screw thread ...
February 9, 2012

physics
The density of ice is 917 kg/m3, and the density of sea water is 1025 kg/m3. A swimming polar bear climbs onto a piece of floating ice that has a volume of 4.41 m3. What is the weight of the heaviest bear that the ice can support without sinking completely beneath the water? ...
February 9, 2012

ap chemistry
for the following, mix the equal volumes of one solution from group I with one solution from group II to achieve the indicated pH. calculate the pH of each solution. Group I: .2M NH4Cl, .2M HCl, .2M C6H5NH3Cl, .2M (C2H5)3NHCl Group II: .2M KOI, .2M NaCN, .2M KOCl, .2M NaNO2 a...
February 9, 2012

Chemistry
Nevermind I actually figured it out. Thank you.
February 7, 2012

Chemistry
Ok when I did the graph I got -2.99e3 as the slope. Is this the answer or do I have to do something else now?
February 7, 2012

Chemistry
The vapor pressure of the liquid HF is measured at different temperatures. The following vapor pressure data are obtained. Temperature(K) Pressure mmHg 250 129.63 260 206.65 270 318.22 280 475.16 Determine the enthalpy of vaporization. I have know idea how to start this. Thank...
February 7, 2012

Chemistry
ln 555.6/281.1 = -deltaH vap/8.314J/k mol [1/256.1K - 1/242K]. I have to solve for delta Hvap. I know that the left side would be7.21. I am not sure what step to do next.
February 7, 2012

physics
n boat starts from rest and accelerates at a constant rate to a final speed of 28 m/s over a distance of 780 m. How much time will this take?
February 6, 2012

Chemistry
Ok thank you. I know what I was doing wrong. I was just hitting the e^x button and I was getting a different answer. I have to hit the 2nd button first and then e^x on my calculator.
February 6, 2012

Chemistry
ln p2/368.3 mm Hg = -24900 J/mol / 8.314 J/k mol [1/259.7K - 1/247.4K] I am having trouble doing the mathto solve for p2. Chemistry - DrBob222, Sunday, February 5, 2012 at 12:44pm The easy way is to calculate 1/259 = ? and 1/247 = ?, then subtract them and multiply that by -...
February 6, 2012

geometry
ABCD is a rhombus with diagonals intersecting at E. If m<ABC is three times m<BAD, find m< EBC
February 5, 2012

Chemistry(Please help, thank you)
Thank you
February 5, 2012

Chemistry(Please help, thank you)
1/2.165 = sqrt x/131.29. I am not sure how to solve for x.
February 5, 2012

Chemistry
1/2.165 = sqrt x/131.29. I am not sure how to solve for x.
February 5, 2012

Chemistry
I got 23.6. Is this correct?
February 5, 2012

Chemistry
The heat of vaporization of benzene, C6H6, is 30.8kJ/mol at its boiling point of 80.1 degrees celsius. How much energy in the form of heat is required to vaporize 102g of benzene at its boiling point? I know that the answer is 24.2kJ but i am not sure how to get this.
February 5, 2012

Chemistry
For some reason on my computer the answer that was posted was sort of cut of so I had a hard time reading it but when I did 1/259 - 1/247 I got -0.00018 then I multiplied by -24900 and divided by 8.314 and got 0.539. Then I took the sqrt of this number and ended up with p2/368...
February 5, 2012

Chemistry
ln p2/368.3 mm Hg = -24900 J/mol / 8.314 J/k mol [1/259.7K - 1/247.4K] I am having trouble doing the mathto solve for p2.
February 5, 2012

Physics
Thank you for your help!
February 5, 2012

Physics
(a) How much heat in kcal must be provided for a 0.853 kg block of lead to raise the temperature of 0.015 kg block of ice from -5ºC to 0ºC? (b) How much heat in kcal must be provided for a 0.853 kg block of lead to melt a 0.015 kg block of ice from at 0ºC? (c) ...
February 5, 2012

Chemistry
The following thermochemical equation is for the reaction of iron(s) with chlorine(g) to form iron(III) chloride. 2Fe(s) + 3Cl2(g) 2FeCl3(s) H = -799 kJ How many grams of Fe(s) would have to react to produce 107 kJ of energy? I am not sure how to start this.
February 4, 2012

Chemistry(Please help, thank you)
Find the value of delta H net for the following equation: SnBr2(s) + TiCl4(l) -> TiBr2(s) + SnCl4(l) Use the following reactions to help solve for the net value: 1) SnCl2(s) + TiBr2(s) -> SnBr2(s) + Ticl2(s) Delta H=+4.2 2) SnCl2(s) + Cl2(g) -> TiCl4(l) deltaH=-195 3...
February 4, 2012

Chemistry
Find the value of delta H net for the following equation: SnBr2(s) + TiCl4(l) -> TiBr2(s) + SnCl4(l) Use the following reactions to help solve for the net value: 1) SnCl2(s) + TiBr2(s) -> SnBr2(s) + Ticl2(s) Delta H=+4.2 2) SnCl2(s) + Cl2(g) -> TiCl4(l) deltaH=-195 3...
February 4, 2012

Physics
The heat of fusion of water is 80 cal/g. When 25 g of ice at 0ºC is placed in the contents of a 12 oz can of Coke (≈350 g) at 25ºC, what is the final temperature of the beverage?
February 4, 2012

Physics
Eighty calories must be added to one gram of ice at 0ºC to melt it. What is the approximate mechanical equivalent of this amount of energy?
February 4, 2012

Poetry
Thanks
February 4, 2012

Poetry
Without knowing the context of of the poem, does this poem title stand out to you, get your attention, and sound good? He Makes Our Joy Full also. do you normally capitalize all words in a poems title or is that just for books? thanks:)
February 4, 2012

Chemistry
I dont know if this will help but I realized there was more information for the problem. 1) SnCl2(s) + TiBr2(s) -> SnBr2(s) + Ticl2(s) Delta H=+4.2 2) SnCl2(s) + Cl2(g) -> TiCl4(l) deltaH=-195 3) TiCl2(s) + Cl2(g) ->TiCl4(l) deltaH=-273 SnCl2(s) + Cl2(g) -> SnCl4(l...
February 3, 2012

Chemistry
Ok well thank you for trying!
February 3, 2012

Chemistry
Find the value of delta H net for the following equation: SnBr2(s) + TiCl4(l) -> TiBr2(s) + SnCl4(l) I know that I already posted this once but I am still lost on what to do. I know that TiCl4=-804.2 and SnCl4=-511.3 but I thought that the values for SnBr2 is 0 as well as ...
February 3, 2012

speech
What is the diference between formal and technical language in speech? thanks
February 2, 2012

Chemistry
How should I go about solving this problem? Am I missing information?
February 1, 2012

Chemistry
Find the value of delta H net for the following equation: SnBr2(s) + TiCl4(l) -> TiBr2(s) + SnCl4(l) I know that I already posted this once but I am still lost on what to do. I know that TiCl4=-804.2 and SnCl4=-511.3 but I thought that the values for SnBr2 is 0 as well as ...
February 1, 2012

Chemistry
How many kilograms of water at 15oC can be heated to 95oC by burning 143 grams of methane, CH4, assuming that 100% of the heat is used to heat the water. The heat of combustion of methane is 891 kJ per mole of methane. (The specific heat of water is 4.184 J/goC.) I am not sure...
January 30, 2012

Chemistry
ok thank you!!
January 30, 2012

Chemistry
Why is it that the straight chain is higher?
January 30, 2012

Chemistry
1)Which compound below would be expected to have the highest boiling point? a) CH3-CH2-CH2-CH2-CH2-CH2-CH3 b) CH3-CH2-CH2-CH2-CH-CH3 | CH3 c) CH3-CH-CH2-CH-CH3 | | CH3 CH3 d) CH3 | CH3-CH-C-CH3 | | CH3 CH3 Do I use molar mass to determine which is the highest?
January 30, 2012

Chemistry
oh ok I understand now, thank you for your help!
January 30, 2012

Chemistry
1) Three factors control the rate of evaporation of a liquid: surface area, temperature, and strengths of intermolecular forces. More than one of the statements given described a correct effect. The statements are (1) the larger the surface area, the faster the rate of ...
January 30, 2012

Chemistry
ok
January 29, 2012

Chemistry
for TiCl4 i got -804.2 and for SnCl4 I got -511.3 and then i subtracted them to get -292.9 but I dont think this is right.
January 29, 2012

Chemistry
1) Determine the value of delta H net for the following equation: SnBr2(s) + TiCl4(l) -> TiBr2(s) + SnCl4(l) I am not sure how to solve this.
January 29, 2012

Chemistry
1) Given the following “substances” and their normal boiling points, in celsius. G:43.8 Celsius J:93.7 M:56.7 T: 83.5 R:63.6 Which set below correctly lists some of these liquids in order of increasing intermolecular forces at 20 oC? a) G < R < J b) J < T &...
January 29, 2012

Chemistry
Is number 1 correct because I thought that was the one that was incorrect?
January 29, 2012

Chemistry
1) Three factors control the rate of evaporation of a liquid: surface area, temperature, and strengths of intermolecular forces. More than one of the statements given described a correct effect. The statements are (1) the larger the surface area, the faster the rate of ...
January 29, 2012

Chemistry
1) Which of the following molecular solids will exhibit dipole-dipole intermolecular forces: NH3, BF3, I2 and H2S? a) NH3, and H2S (correct) b) NH3, BF3, and H2S (BF3 has polar bonds, but is a nonpolar molecule) c) I2 only d) BF3 and I2 e) NH3, BF3, I2 and H2S I think that ...
January 29, 2012

Chemistry
1) The order of the boiling points for the hydrogen halides, except for HF, is HI > HBr > HCl. The reason for this order can be attributed to a) the relative covalent bond strengths. b) differences in hydrogen bonding. c) differences in dipole-dipole attractions. d) ...
January 29, 2012

Chemistry
1) Which one of the following molecules is the most polarizable? a) H3C – I b) H3C – CH3 c) H3C – F d) H3C – H e) H3C – OH I chose H3C-I as the answer because the mm was the greatest. I added the mm of H, C, and I and got 141.934. Did I do this ...
January 29, 2012

Chemistry
So choice b is not correct either?
January 29, 2012

Chemistry
1. Which of the following statements concerning dipole-dipole attractions is correct? a) Dipole-dipole attraction is a weaker force than covalent bonds, being about 50% as strong. b) Dipole-dipole attractions increase as the distance between the dipoles increase. c) Dipole-...
January 29, 2012

Chemistry(Please check)
1) Which one of the following molecules is the most polarizable? a) H3C – I b) H3C – CH3 c) H3C – F d) H3C – H e) H3C – OH I chose H3C-I as the answer because the mm was the greatest. I added the mm of H, C, and I and got 141.934. Did I do this correctly?
January 29, 2012

Chemistry
Ok so would you say just high boiling point and low vapor pressure?
January 29, 2012

Chemistry
1) Which of the following properties of water can be explained using hydrogen bonding arguments? 1. its ability to dissolve most ionic compounds. 2. its high boiling point. 3. its low vapor pressure a) only 1 or only 2 or only 3 b) 1 and 2 only c) 1 and 3 only d) 2 and 3 only...
January 29, 2012

Physics
A weight lifter performs a clean and jerk on 150 kg, raising it 2 m above the ground in 1.5 s. What is his power output during the lift?
January 29, 2012

Chemistry(Please check)
1) Which of the following properties of water can be explained using hydrogen bonding arguments? 1. its ability to dissolve most ionic compounds. 2. its high boiling point. 3. its low vapor pressure a) only 1 or only 2 or only 3 b) 1 and 2 only c) 1 and 3 only d) 2 and 3 only ...
January 29, 2012

Chemistry(Please check)
Oh ok thank you I will look over it again.
January 28, 2012

Chemistry(Please check)
1) Where in the phase diagram of a compound do all phases exist together? a) at the sublimation point b) at the boiling point c) at the melting point d) at the critical point e) at the triple point I chose answer E, the triple point. Is this correct?
January 28, 2012

Chemistry(Please check)
ok thank you
January 28, 2012

Chemistry(Please check)
O ok so it is london forces,dipole,then hydrogen?
January 28, 2012

Chemistry(Please check)
1) For a series of small molecules of comparable molecular mass, which of the following choices lists the intermolecular forces in the correct increasing order? a) dipole-dipole forces < London forces < hydrogen bonds b) hydrogen bonds < dipole-dipole forces < ...
January 28, 2012

English
its number one...
January 26, 2012

physics
Sound travels around 340 m/s in air. If a bat squeaks and hears the echo of its squeak return to it 6 seconds later, how far away is the insect which the bats squeak encountered? This question doesnt even make sense to me!! Does anyone have a formula that I can use to try and ...
January 25, 2012

physics
Sound travels around 340 m/s in air. If a bat squeaks and hears the echo of its squeak return to it 6 seconds later, how far away is the insect which the bats squeak encountered? This question doesnt even make sense to me!! Does anyone have a formula that I can use to try and ...
January 25, 2012

Chemistry
Ok thank you for your help!!
January 22, 2012

Chemistry
An insulated beaker contains 250g of water at 25 degrees celsius. Exactly 41.6g of a metal at 100 degrees celsius was dropped in the beaker. The final temperature of the water was 26.4 degrees celsius. Assuming that no heat is lost in any other way, calculate the specific heat...
January 22, 2012

Chemistry
A chemical reaction is run in which 132 joules of work is done by the system amd the internal energy changes by 469 joules. Calculate the amount of heat transferred. u=q+w I was going to do 469 = q + 132 but I think this is wrong.
January 22, 2012

Chemistry
Ok thank you for your help!
January 22, 2012

Chemistry
I did 30kJ X 26.9815/4.00 = 202.36 One of the anser choices that is given is -202 kJ. Is this incorrect or did I do the calculation wrong?
January 22, 2012

Chemistry
For the reaction Al(s) + 3 HCl(aq)->AlCl3(s) +3/2 H2(g) it was observed that when 4.00g of aluminum reacted with excess HCl, exactly 30,0 kJ of heat was released. What is the delta H for this reaction? I do not understand how to get the delta H value.
January 22, 2012

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