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September 22, 2014

Homework Help: Science: Chemistry

Recent Homework Questions About Chemistry

Post a New Question | Current Questions

Chemistry
A laser produces 15.0mW of light. In 3.00hr , the laser emits 4.53×1020 photons. What is the wavelength of the laser?
Monday, September 15, 2014 at 3:23pm

Chemistry
A proton in a linear accelerator has a de Broglie wavelength of 115pm. What is the speed of the proton?
Monday, September 15, 2014 at 3:22pm

Chemistry
An electron has an uncertainty in its position of 611pm. What is the uncertainty in its velocity?
Monday, September 15, 2014 at 3:21pm

Chemistry: Please Help!!
39. Explain why sweating cools you down in terms of molecular kinetic energy. 40. You take a pizza out of the oven and let it cool briefly. When you bite into it, the crust is not too hot but the cheese burns your mouth. Explain why this happens in terms of specific heat ...
Monday, September 15, 2014 at 3:08pm

Chemistry: Please Help!!
37. Lake Michigan is a very large, very deep body of water, located in a region of the United States that gets quite cold in winter. On the coldest day of last year, what was the temperature at the bottom of the lake. Explain your answer in terms of density of water. 38. ...
Monday, September 15, 2014 at 3:05pm

Chemistry
B. Could non-polar nitrogen molecules and polar water molecules form bonds with one another? if so, what kind? C. Given your answer to B above, do you think that there is a great deal of N2 dissolved in the oceans, a small amount, or none at all?
Monday, September 15, 2014 at 2:52pm

Chemistry
At 27 degrees celcius, nitrogen has a volume of 650 cm^3 under a pressure of 980 mmHg. What would be its volume at the same temperature but at a pressure of 760 mmHg?
Monday, September 15, 2014 at 2:52pm

Pure Chemistry
At 27 degrees celcius, nitrogen has a volume of 650cm^3 under a pressure of 980mmHg. What would be its volume at the same temperature but at a pressure of 760mmhg ?
Monday, September 15, 2014 at 2:04pm

chemistry
If an irregular object displaces 10mL of water within a graduated cylinder and its density is known as 2.5 g/mL. What is the mass of the object?
Monday, September 15, 2014 at 1:22pm

chemistry
Nickel is about 2 millimeter thick or 2/1000 of a meter.how many nanometer is this?
Monday, September 15, 2014 at 1:18pm

Chemistry
Diluting and dissolving of potassium nitrate is very endothermic.Suggest what would be observed to the temperature if 2.0g of the salt is added to 2cm3 of water.
Monday, September 15, 2014 at 12:29pm

chemistry
The observation for three materials shows: Material A absorbs all the visible light (opaque) Material B is transparent to all the visible light (transparent) Material C absorbs blue light but is transparent to red light. (Blue light has wavelength 0.4 m, red light has ...
Monday, September 15, 2014 at 10:47am

Chemistry
How much heat will be released when 0.750 moles of carbon monoxide (CO) react in an excess of oxygen gas? 2CO(g) + O2(g) ¨ 2CO2(g) + 566 kJ
Monday, September 15, 2014 at 9:57am

chemistry 1045L
The volume of a sphere is given by V=(4)(3.14)(r^3)/3 where r is the radius of the sphere. what is the density in g/mL of a sphere which weighs 2.00lb and has a radius of 3.50 inches?
Monday, September 15, 2014 at 9:34am

chemistry
how much copper sulphate will require saturating 80 grams of water at 20 degree celcious .if solubility of copper sulphate at 20degree celcious is 25?
Monday, September 15, 2014 at 8:34am

Chemistry
How do we do charge balance and mass balance? Plz give me an answer on a general basis so that i can do it for any compound i get. Thanks
Monday, September 15, 2014 at 2:46am

chemistry
If it costs $3.92 for a gallon of gas, and I fill up with 13.5 gallons once each 1.5 weeks, how much am I spending on gas in a 5 week month?
Sunday, September 14, 2014 at 10:36pm

chemistry
How many grams of Cu (s) are needed to form 6.00g Ag from a solution of AgNO3? The reaction is Cu (s)+2Ag^+(ag)--> Cu^2+(aq)+2Ag (s) the molar masses are: Ag=107.868 and Cu=63.546g
Sunday, September 14, 2014 at 10:33pm

Chemistry
If the edge length of an NaH unit cell is 488pm, what is the length (in picometers) of an Na−H bond? Na−H has face-centered cubic unit cell. Please help
Sunday, September 14, 2014 at 7:44pm

Chemistry
An element crystallizes in a body-centered cubic lattice. The edge of the unit cell is 3.13Å , and the density of the crystal is 7.78g/cm3. Calculate the atomic weight of the element. Please help, thanks
Sunday, September 14, 2014 at 7:41pm

chemistry
For the decompostion of gaseous dinitrogen pentaoxide, 2N2O5(g)--->4NO2(g) +O2(g) . The rate constant is k=2.8 x 10^-3 at 60 degrees C. The initial concentration of N2O5 is 2.45 mol/L. What is (N2o5) after 5.00 min? What fraction of the N2o5 has decomposed after 5 min?
Sunday, September 14, 2014 at 7:30pm

chemistry
By what factor does the fraction of collisions with energy equal to or greater than activation energy at 100 kJ/mol. change if the temperature increases from 32 degrees celsius to 63 degrees celsius. Give your answer in SCIENTIFIC NOTATION
Sunday, September 14, 2014 at 7:29pm

College Chemistry
how many liters of ethanol contain 1.5 kg of ethonal?
Sunday, September 14, 2014 at 7:29pm

Chemistry Urgent Help and Check Please!
a) You use 100 ml ethylchloride (density 0.92 g/ml) to extract 25 ml ethylene bromohydrin (density 2.41 g/ml) mixed with 100 ml. Is the aqueous layer the lower or the upper layer. How could you easily test this. ----- Ethylchloride is less dense so it is the top layer Ethylene...
Sunday, September 14, 2014 at 7:06pm

chemistry
2 HI(g)--><--H2(g) + I2(g) When a sufficiently large sample of HI(g) is introduced into an evacuated vessel at 643 K, the equilibrium concentration of I2(g) is found to be 0.248 M. Calculate the concentration of HI in the equilibrium mixture. M. Please help! I have no ...
Sunday, September 14, 2014 at 6:24pm

Chemistry
What is 100mL of water + 45.00g of ice?
Sunday, September 14, 2014 at 5:14pm

chemistry
Calculate the following quantity: Volume in mL of 21.4 M cobalt(II) chloride solution that must be diluted with water to prepare 17 mL of an 51.5 M solution. Calculate to 0 decimal places and do not include units. Also, do NOT use scientific notation.
Sunday, September 14, 2014 at 5:12pm

chemistry
Discuss the difference in lattice enthalpy between NaCl and CsF
Sunday, September 14, 2014 at 5:02pm

chemistry
The temperature of a substance ____ as its heat of fusion is added to melt the substance A. increases B. decreases C. remains constant D. fluctuates from rapid increases and decreases
Sunday, September 14, 2014 at 3:51pm

chemistry
According to Boyle, pressure and volume of a confined gas are ____ proportional, and according to Charles, the volume of a gas at a constant pressure is____ proportional to its Kelvin temperature. A. directly; inversely B. directly; not C. inversely; directly D. not; inversely
Sunday, September 14, 2014 at 3:44pm

chemistry
What is the molecular mass of potassium hydrogen carbonate (KHCO3)? A. 110g/mol B. 84g/mol C. 68g/mol D. 116g/mol
Sunday, September 14, 2014 at 3:16pm

chemistry
What mass of sulfur has to burn to produce 4.5L SO2 at 300°C and 101 kPa in the following reaction? S(s) + O2(g) -> SO2(g) A. 3.07 g S B. 41.0 g S C. 13.5 g S D. 68.8 g S
Sunday, September 14, 2014 at 3:03pm

chemistry
What mass of sulfur has to burn to produce 4.5L SO2 at 300°C and 101 kPa in the following reaction? S(s) + O2(g) -> SO2(g) A. 3.07 g S B. 41.0 g S C. 13.5 g S D. 68.8 g S
Sunday, September 14, 2014 at 3:03pm

Chemistry Urgent Help Please!
If caffeine is soluble in hot benzene but insoluble in hot petroleum ether, how could you use this information to design a crystallization procedure?
Sunday, September 14, 2014 at 1:51pm

chemistry
The observation for three materials shows: Material A absorbs all the visible light (opaque) Material B is transparent to all the visible light (transparent) Material C absorbs blue light but is transparent to red light. (Blue light has wavelength 0.4 m, red light has ...
Sunday, September 14, 2014 at 12:30pm

Chemistry
If 64.0 g of H2O are actually obtained, find the actual yield %. Show that the % the same whether you calculate using grams or moles. Theoretical yield is 4.04 moles and in grams is 72.80 grams 2H2 + 1O2=2H2O
Sunday, September 14, 2014 at 12:20pm

Chemistry
Suppose the atomic mass unit had been defined as 1/10 th of the average mass of an atom of phosphorus. What would the atomic mass of Carbon be on this scale. What would Avogadro's number be?
Sunday, September 14, 2014 at 9:22am

Chemistry Urgent Help Please!
You use 100 ml ethylchloride (density 0.92 g/ml) to extract 25 ml ethylene bromohydrin (density 2.41 g/ml) mixed with 100 ml. Is the aqueous layer the lower or the upper layer. How could you easily test this. You dissolve sodium chloride 40g. in the above mixture. Assuming the...
Sunday, September 14, 2014 at 1:05am

Chemistry
What is the velocity of an electron that has a de Broglie wavelength approximately the length of a chemical bond? Assume this length to be 2.5×10−10m .
Saturday, September 13, 2014 at 11:57pm

chemistry
suggest an alternative indicator for the standardization reaction. Explain the rationale behind your choice.
Saturday, September 13, 2014 at 11:22pm

Chemistry
A metal bar having a mass of 212 g is heated to 125.0°C and then dropped into 375 g of water at 24°C. After a while the temperature of the water and the metal is 34.2°C. If the specific heat of the metal is 0.831 J/g°C, how much heat did the metal lose? Please ...
Saturday, September 13, 2014 at 9:42pm

Chemistry
4. Suppose there are 72.0 g of O2 available, along with the 8.08 grams of H2. Use ratios of stoichiometric coefficients to find the limiting reagent for the reaction. Then, find the theoretical yield in both moles and grams. 2H2 + 1O2 à 2H2O I got 2.25 grams for o2 Then...
Saturday, September 13, 2014 at 9:10pm

chemistry
Which element's atomic radius changes the most in size when it becomes ionized? A. Fluorine B. Lithium C. Sodium D. Chlorine
Saturday, September 13, 2014 at 8:30pm

Chemistry
For the reaction 2H2 + 1O2 à 2H2O, there are 8.08 grams of H2 available. 2. Use the ratio of stoichiometric coefficients in the reaction above to determine how many moles of H2O can be produced from the H2 available. Then, use molar mass to convert the moles of H2O into...
Saturday, September 13, 2014 at 8:26pm

chemistry
Covalent bonding (with an electronegativity difference below 0.5) results when fluorine bonds with A. hydrogen B. potassium C. iodine D. fluorine
Saturday, September 13, 2014 at 8:19pm

chemistry
What is the electronegativity difference for a bond between potassium and iodine? A. 3.3 B. 0.4 C. 4.6 D.1.7
Saturday, September 13, 2014 at 8:15pm

chemistry
Which of the following is true? A. Group 1 elements are more reactive than the group 2 elements because they have more valence to lose. B.Lithium is the least reactive element in group, because its valence electron is held more tightly than the others in the same group. C. ...
Saturday, September 13, 2014 at 8:04pm

chemistry
What type of reaction does the following equation represent? AgNO3 + NaCl ---> AgCl + NaNO3 A. Single-displacement reaction B. Synthesis C. Combustion D. Double-displacement reaction
Saturday, September 13, 2014 at 7:50pm

chemistry
What type of reaction does the following equation represent? AgNO3 + NaCl ---> AgCl + NaNO3 A. Single-displacement reaction B. Synthesis C. Combustion D. Double-displacement reaction
Saturday, September 13, 2014 at 7:50pm

chemistry
What type of reaction does the following equation represent? AgNO3 + NaCl ---> AgCl + NaNO3 A. Single-displacement reaction B. Synthesis C. Combustion D. Double-displacement reaction
Saturday, September 13, 2014 at 7:50pm

chemistry
The ionic radii of Na+ (atomic weight 22.99) and Cl- (atomic weight 35.45) are 1.0 and 1.8 Angstrom, respectively. Treating the ions as hard spheres, calculate the density of NaCl. Compare this with the measured density of 2.17 g/cm3.
Saturday, September 13, 2014 at 7:48pm

chemistry
The typical person needs a 2000 calorie diet to sustain “normal” activity. Nowadays, a lot of the energy in American diet comes from fats and sugars. Assume that “fats” provide 9.0 calories per gram and sugars (treat as glucose) provide 4.5 calories per ...
Saturday, September 13, 2014 at 7:39pm

Chemistry
A metal bar having a mass of 212 g is heated to 125.0°C and then dropped into 375 g of water at 24°C. After a while the temperature of the water and the metal is 34.2°C. If the specific heat of the metal is 0.831 J/g°C, how much heat did the metal lose?
Saturday, September 13, 2014 at 7:20pm

Chemistry
For the following equation, write a thermochemical equation that includes an energy term within the equation: The formation of 1 mol of copper(II)chloride from its elements releases 220.1kJ of energy.
Saturday, September 13, 2014 at 4:00pm

Chemistry
a gold bar weighing 33.5 g and having an initial temperature of 25.0 Celsius absorbs 5000 J of heat. What would the new temperature be?
Saturday, September 13, 2014 at 3:49pm

chemistry
3. Use the ratio of stoichiometric coefficients in the reaction above to determine how many moles of O2 will react with the H2 available. Then, use molar mass to convert the moles of O2 into grams. For the reaction 2H2 + 1O2 =2H2O, there are 8.08 grams of H2 available. the ...
Saturday, September 13, 2014 at 2:41pm

Chemistry
Rewrite the following using a thermochemical equation with a deltaH value: a) The standard molar enthalpy of combustion for propane is -2220kJ/ mol.
Saturday, September 13, 2014 at 2:13pm

Chemistry
A plumber installs a pipe that has a diameter of 10 cm and a length of 2.4m, Calcualte the volume of water(in cm3) that the pipe will hold. Express your answer to the correct number of significant digits. Note: The formula for the volume of a cylinder is V=Pi(r)2h, where r is ...
Saturday, September 13, 2014 at 1:55pm

Chemistry
Calculate the solubility of 43g of NaCl containing 100ml of water at temperature of 20 degrees
Saturday, September 13, 2014 at 1:18pm

Chemistry
How much Tris do you need to weigh out to make 250 ml of the 50 mM buffer? A. 0.95g B. 1.51g C. 2.42 D. 1.75g
Saturday, September 13, 2014 at 10:42am

Analytical Chemistry
principles behind the dilution and aliquoting of the NaOH solution
Saturday, September 13, 2014 at 2:37am

chemistry
How much of each solution will you need to mix to obtain 100 – 120 ml of 20 mM buffer pH 4.0? A. 35 ml sodium acetate + 90 ml acetic acid B. 100 ml sodium acetate + 16 ml acetic acid C. 16 ml sodium acetate + 100 ml acetic acid D. 90 ml sodium acetate + 35 ml acetic acid
Friday, September 12, 2014 at 11:05pm

Chemicals of Life/Chemistry
Which weighs more: a liter of water at 20 degrees C or a liter of water at 80 degrees C. Explain.
Friday, September 12, 2014 at 9:38pm

chemistry
3. Describe the subatomic structure of the nucleus of carbon-14, including the structure of each nucleon. Draw a picture. Describe the forces that hold the nucleus together and draw them on your diagram. Write the equation for the carbon-14 isotope decay by beta emission. ...
Friday, September 12, 2014 at 6:21pm

Chemistry
A portable electric water heater transfers 255 watts (W of power to 5.5 L of water, where 1 W=1J/s.How much time (in minutes) will it take for the water heater to heat the 5.5 L of water from 27∘C to 49∘C? (Assume that the water has a density of 1.0 g/mL.
Friday, September 12, 2014 at 6:20pm

chemistry
25.6mL of ethanol (density =0.789 g/mL) initially at 5.4∘C is mixed with 30.4mL of water (density = 1.0 g/mL) initially at 20.4∘C in an insulated beaker.Assuming that no heat is lost, what is the final temperature of the mixture?
Friday, September 12, 2014 at 6:18pm

chemistry
How many kilowatt-hours of energy are necessary to heat the air in the house from 9∘C to 30∘C? The heat capacity of air is 1.03 J/g∘C.A room contains 45kg of air.
Friday, September 12, 2014 at 6:16pm

chemistry
Calculate the final temperature of 30mL of ethanol initially at 15∘C upon absorption of 913J of heat. (density of ethanol =0.789 g/mL)
Friday, September 12, 2014 at 6:13pm

Chemistry 1300
1) Aluminum metal reacts with chlorine gas to form solid aluminum trichloride, AlCl3. What mass of chlorine gas (Cl2) is needed to react completely with 163 g of aluminum? 2) Magnesium (used in the manufacture of light alloys) reacts with iron(III) chloride to form magnesium ...
Friday, September 12, 2014 at 4:36pm

Chemistry
3. The Haber–Bosch process for fixation of nitrogen is one of the more important chemical reactions ever invented. Without the invention of this process, which is used to make ammonia for fertilizer, the world’s population would not be as large as it is today. N2(g...
Friday, September 12, 2014 at 4:34pm

Chemistry, Help!
a) A 750-mL sample of hydrogen exerts a pressure of 822 torr at 325 K. What pressure does it exert if the temperature is raised to 475 K at constant volume? b) Aluminum oxide, Al2O3, is used as a filler for paints and varnishes as well as in the manufacture of electrical ...
Friday, September 12, 2014 at 4:32pm

chemistry
The density of pure copper is 8.96 at 20°C. If 6.50 g of pure copper pellets is added to a graduated cylinder containing 13.4 mL of water, to what volume level will the water in the cylinder rise
Friday, September 12, 2014 at 4:20pm

organic chemistry
or perhaps comparable over the counter?
Friday, September 12, 2014 at 11:06am

organic chemistry
Can a person be able to find some 1-Pentanamine (Y = NH2 over the counter ?
Friday, September 12, 2014 at 11:03am

chemistry
when 21.6g of carbon were burned in the presence of 73.9g of oxygen 16.3g of oxygen remain unreacted. What mass of carbon dioxide was produced
Friday, September 12, 2014 at 8:59am

CHEMISTRY
How do the indicators work , by changing color ?
Friday, September 12, 2014 at 6:21am

CHEMISTRY
How can we determine the equivalence point ( or end point ) in the curves in titration ( strong acid/weak base and weak acid/strong base )
Friday, September 12, 2014 at 12:36am

Chemistry please help
Complete each calculation. Express your answer to the correct number of significant digits. a)4.02mL + 3.76mL +0.95mL b)(2.7 x 10^2m) x (4.23 x 10^2m) c)5092kg divided by 23L d) 2-6.3 + 6-7 e)(6.853 x 10^3L) + (5.40 x 10^3mL) f)(572.3g + 794.1g) divided (24mL + 52mL) My ...
Thursday, September 11, 2014 at 9:20pm

chemistry
solution of 0.1molar NH4OH and 0.1 NH4CL ph=9.25 calculate kb for NH4OH?
Thursday, September 11, 2014 at 9:13pm

Chemistry
A 5 oz carrot is burned in a calorimeter containing 10.0 lb of water. The water heats up from 20.5 oC to 22.8 oC. How many Calories are in the 5 oz carrot? Round to correct sig. fig. 1 Cal = 1000 cal.
Thursday, September 11, 2014 at 9:11pm

Chemistry
A frozen dinner contains 1.5 g of fat, 14 g of carbohydrates, and 11 g of protein. How much energy is contained in this meal? Food energy Carbohydrate 4kcal/g Fat 9kcal/g protein 4kcal/g
Thursday, September 11, 2014 at 9:10pm

Chemistry
If 155 J of energy is added to 18.5 g of silver, how much will the temperature rise? Silver Specific Heat= (0.235J/g deg C)
Thursday, September 11, 2014 at 9:08pm

Chemistry
If we heat a 10 g sample of gold and a 10 g sample of iron with 50 kJ of energy each, which will have the greatest change in temperature? gold specific heat= 0.129J/g degC) iron specific heat = (0.452 J/g degC)
Thursday, September 11, 2014 at 9:05pm

Chemistry
Complete each calculation. Express your answer to the correct number of significant digits. a)4.02mL + 3.76mL +0.95mL b)(2.7 x 10^2m) x (4.23 x 10^2m) c)5092kg divided by 23L d) 2-6.3 + 6-7 e)(6.853 x 10^3L) + (5.40 x 10^3mL) f)(572.3g + 794.1g) divided (24mL + 52mL) My ...
Thursday, September 11, 2014 at 8:17pm

chemistry :)
Write the formula for the polyatomic ion in NaNO 3. Write the formula for the polyatomic ion in Ag2CO3. Write the formula for the polyatomic ion in NaHCO3. Write the formula for the polyatomic ion in BaSO4
Thursday, September 11, 2014 at 8:04pm

college chemistry
Express the concentration of a 0.0620M aqueous solution of fluoride, F-, in mass percentage and in parts per million. assume the density of the solution is 1.00g/mL.
Thursday, September 11, 2014 at 7:29pm

chemistry
which of the following is true regarding the transition elements? A. Multiple oxidation states resulting from the involvement of d electrons in bonding is a characteristic of transition elements. B. Most transition elements have lower melting and boiling points than the main ...
Thursday, September 11, 2014 at 5:12pm

chemistry
If you have 0.833g of copper(II) sulfate, how many moles doo you have?
Thursday, September 11, 2014 at 2:08pm

CHEMISTRY
What is difference between equivalence point and end point in the titration ?
Thursday, September 11, 2014 at 11:28am

CHEMISTRY
What indicator is better in the following titrations : 1) strong acid/strong base a) methyl red (4.4 - 6.2 ) b) bromophenol blue (6.2 - 7.6 ) 2) strong acid/weak base a) methyl orange (3.1 - 4.4 ) b) bromophenol blue (3.0 - 4.6 ) 3) weak acid/strong a) phenolphthalein (8.0 - ...
Thursday, September 11, 2014 at 11:25am

CHEMISTRY
Determine the solvent and solute in the following : a) carat 14 gold b) gaseous drinking ( pepsi for ex.)
Thursday, September 11, 2014 at 11:18am

CHEMISTRY
Classify these mixtures to homogeneous and heterogeneous a) orange juice b) tap water ( home water )
Thursday, September 11, 2014 at 11:14am

Chemistry
If there are 0.625 g of NaCl left in a beaker that originally contained 75.0 mL of saltwater, what must have been the molar concentration of the original solution? The molar mass of NaCl is 58.44 g/mol.
Thursday, September 11, 2014 at 10:54am

chemistry
mercury has a specific gravity of 13.6.How many mL OF mercury have a mass of 0.35kg.
Thursday, September 11, 2014 at 9:44am

chemistry
Calculate the ÄHvap , in kJ/mol, for ethanol, given that the vapor pressure at 45.0°C is 155.0 torr. The normal boiling point of ethanol is 78°C. Express your answer to two decimal places.
Thursday, September 11, 2014 at 9:29am

Chemistry please help
104 ml of ethene, C2H4 is burned in 408 ml of oxygen, producing carbon dioxide and some liquid water. Some oxygen remain unreacted. Calculate the volume of carbon dioxide produced and the volume of oxygen remaining
Thursday, September 11, 2014 at 7:06am

Chemistry - dilutions
The concentration of stain in the bottle was 5% and you added 100 microliters of it to 9.9ml of a buffer to make a working dilution of stain. You then combined 10 microliters of that diluted stain with 40 microliters of your diluted cells and put a few microliters of that ...
Thursday, September 11, 2014 at 2:18am

Chemistry
the current U.S. penny is only 2.5% copper the remaining portion is zinc. Given the density of copper as 8.94 g/cm and the density of zinc is 6.57 g/cm, calculate the density of a penny.
Thursday, September 11, 2014 at 12:23am

chemistry
If there are 0.561 g of NaCl left in a beaker that originally contained 75.0 mL of saltwater, what must have been the molar concentration of the original solution? The molar mass of NaCl is 58.44 g/mol. Give your answer to 3 decimal places
Wednesday, September 10, 2014 at 9:09pm

Chemistry
If the methane contained in 3.50L of a saturated solution at 25 ∘C was extracted and placed under STP conditions, what volume would it occupy? Solubility of methane is 1.3 millimolar
Wednesday, September 10, 2014 at 8:45pm

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