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November 29, 2014

Homework Help: Science: Chemistry

Recent Homework Questions About Chemistry

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Chemistry
How many mL of a stock 2.50M HCl solution are required to prepare 25.0 mL of a 0.15M HCl solution?
Sunday, November 23, 2014 at 11:14pm

Chemistry
A certain reaction has an equilibrium constant of 0.65. Calculate the constant for the reverse reaction.
Sunday, November 23, 2014 at 11:11pm

chemistry
Use the Henderson-Hasselbalch equation to calculate the pH of a solution that is 0.140M in propanoic acid and 0.120M in potassium propanoate
Sunday, November 23, 2014 at 11:03pm

Chemistry
Calculate the energy (kJ) required to raise the temperature of 22g of water from 12 C to 90 C.
Sunday, November 23, 2014 at 10:02pm

Chemistry
If 120. grams of KClO3 reacts, how many grams of oxygen are produced?
Sunday, November 23, 2014 at 8:34pm

chemistry
Calculate the vapor pressure of a solution containing 28.7g of glycerin (C3H8O3) in 136mL of water at 30.0 ∘C. The vapor pressure of pure water at this temperature is 31.8 torr. Assume that glycerin is not volatile and dissolves molecularly (i.e., it is not ionic) and ...
Sunday, November 23, 2014 at 8:32pm

Chemistry - Heat of Fusion of Ice
I need help with these questions since the lab report needs to be completed like...NOW >_< We were supposed to experimentally determine the heat of fusion of ice and compare it to the accepted value as listed in your reference table.Please help me: Does the value depend ...
Sunday, November 23, 2014 at 8:10pm

chemistry
What mass of rhodium contains as many atoms as there are zirconium atoms in 23 g of zirconium?
Sunday, November 23, 2014 at 6:45pm

Chemistry
The thermite reaction was used to weld rail ties together. If 15.0 grams of aluminum were used, how many grams of ferric oxide would be required? How many grams of molten iron would forma?
Sunday, November 23, 2014 at 6:04pm

Chemistry
Draw all of the possible alkyne isomers of CH≡CCH2CH2CH2CH3.
Sunday, November 23, 2014 at 5:10pm

Chemistry
What volume will 823 mL of SO3 gas at 11 degrees celsius and 720 mm Hg occupy when the pressure is raised to 1.55atm and the temperature is raised to 81 degrees celsius?
Sunday, November 23, 2014 at 4:28pm

chemistry
How many milliliters of 0.413 M NaC2H3O2 are needed to supply 27.3 g NaC2H3O2?
Sunday, November 23, 2014 at 4:01pm

Chemistry
An excess of Al and 7.9 Mole of Br2 are reacted according to the question 2Al+3 Br2 equals 2AlBr3
Sunday, November 23, 2014 at 3:46pm

Chemistry
What mass of AuCl3 contains 160.9 g of gold? My work i got 104.6 g Am i right?
Sunday, November 23, 2014 at 3:18pm

Chemistry
Calculate the pH of a 1.19M sodium formate, HCOONa, solution.
Sunday, November 23, 2014 at 3:17pm

Chemistry
What mass of pure silver would you obtain from 85.0 g of AgNO3? My work The answer i got is 53.55 g Am i right?
Sunday, November 23, 2014 at 3:17pm

Chemistry
Calculate the pH of a buffer solution made by mixing 231 mL of a 1.04M trimethylamine (CH3)3N solution with 176 mL of a 1.38M trimethylammonia chloride, (CH3)3NHCl solution. Enter your answer to TWO decimal places. DO NOT use scientific notation.
Sunday, November 23, 2014 at 2:18pm

chemistry
50ml of 20.8% bacl2 and 100ml of 9.8% h2s04 solutions are mixed. Molarity of cl ions in the resulting solution wt of ba =137 I do not still understand step by step clearly Thank a lot
Sunday, November 23, 2014 at 1:53pm

Chemistry
How many grams of nitric acid (HNO3) must be dissolved in 590 ml of water to make a solution with a pOH = 10.1? Select one: a. 2.9 x 10-9 g b. 7.9 x 10-3 g c. 4.7 x 10-3 g d. 7.9 x 10-6 g e. 7.4 x 10-5 g
Sunday, November 23, 2014 at 1:23pm

chemistry
I have to calculate the ΔV= final volume-initial volume For the first trial the final volume was .005mL the initial volume was .03mL, which equaled to -.025mL. The volume was negative because it was exothermic reaction. For the second trial the final volume was 0.015 and ...
Sunday, November 23, 2014 at 1:10pm

chemistry
The National Institute of Science and Technology (NIST) kinetics database lists the rate constant, k, of a particular gaseous reaction as 8.56× 10–10 cm3·molecule–1·s –1 at 298 K. convert to units of M-1 s-1. convert rate constant to units of...
Sunday, November 23, 2014 at 12:43pm

Chemistry
Calculate the S(univ) for the following phase change at 25 deg celcius. The boiling point of heptane is 98.0 Celcius and has a Delta Hvap= +21.6kj/mol. C7H16(l)--> C7H16(g) Delta S= +79.0j/k I know that the equation is Delta Suniv= DSsys + DSsurr PLEASE SHOW ME HOW TO DO IT...
Sunday, November 23, 2014 at 12:12pm

Chemistry
What is the mole fraction of O2 in a mixture of 15.1g of O2, 8.16g of N2, and 2.46g of H2? (PLEASE EXPLAIN WHAT YOU DO!) Thanks
Sunday, November 23, 2014 at 11:33am

Chemistry
How do you set up this problem? Calculate the volume , in ml of a 0.150 M NaOH soulution needed to neutralize 25.0ml of a 0.288 M HCl solution?
Sunday, November 23, 2014 at 10:46am

Chemistry
In the reaction 2A+B2 to 2AB if 0.5 moles of A and an excess of B are combined and the reaction goes to %100 completion, then how many moles of C are formed?
Sunday, November 23, 2014 at 10:10am

chemistry
2Al (s) + 3Cl2 (g)  2 AlCl3 (s) i)obtain the limiting reagent. when 2.00 mole of Cl2 (g) is reacted with 54.3 g of Al (p). ANSWER : Cl is limiting reagant. 54.3gAl(p)/27 = 2.01AI(P) Initial = 2.01 mol 2 mol divied = 2.01/2 2/3 = 1.005 =0.67 cl is smaller than al . can ...
Sunday, November 23, 2014 at 9:03am

Chemistry
The rusting of iron is represented by the equation 4Fe+3O2=2Fe2O. A 1.45-mol sample of iron, how many moles of Fe2O3 will there be after rusting has completed.
Sunday, November 23, 2014 at 2:23am

Chemistry
Calculate Ecell for reaction for the given info below.. O2(g)+2H2O(l)+4Ag(s)--> 4OH-(aq)+4Ag+(aq Ag+(aq)+ 1e ---> Ag(s) Ered= 0.80v O2(g)+2H2O(l) + 4e ---> 4OH- Ered= 0.40v My confusion is I have done problems similar to this when the Ered was negatives, but two ...
Sunday, November 23, 2014 at 12:43am

chemistry
Draw the three alkenes, each of formula C5H10, that will form 2-methylbutane upon hydrogenation.
Saturday, November 22, 2014 at 11:44pm

chemistry
Poly(methyl methacrylate) (PMMA), more commonly known as acrylic glass.Draw the monomer, given that this polymer forms by addition polymerization. Include all H atoms.
Saturday, November 22, 2014 at 11:44pm

Chemistry
A student was given a 2.45 g of impure potassium sulfate (K2SO4) sample. He dissolved this sample in 100 mL of water first and then added some barium chloride (BaCl2) solution. A 2.15 g of BaSO4 precipitate was obtained at the end of the reaction. What is the percent purity of...
Saturday, November 22, 2014 at 10:41pm

Chemistry
I have an assignment. It has two boxes to model the particles of the same gas at different temperature (18 and 45 degrees Celsius). I have to write two or three sentences relating the temperature, the average kinetic energy, and the motion of the particles in the two boxes. ...
Saturday, November 22, 2014 at 10:27pm

Chemistry
If I had a question about complex ions and the problem had a "mixture" of two compounds, how would I know if one of the products formed is going to be a solid or liquid? I know there are solubility rules, but is there something else you can use to tell?
Saturday, November 22, 2014 at 10:22pm

Chemistry
What is the mass of a sample of (NH4)2SO4 that contains 8.01 x 10^24 atoms of oxygen
Saturday, November 22, 2014 at 10:01pm

Chemistry
Calculate the volume of concentrated reagent required to prepare the diluted solution 17 M H3PO4 to prepare 939 mL of 6.7 M H3PO4
Saturday, November 22, 2014 at 9:53pm

physical chemistry
Please prepare 0.5L of 1.2M HCl in 50% (v/v) aqueous methanol. The details of HCl are as follows: Hydrochloric acid: Purity : 36%-38% Density : 1.18g/mL Physical state : liquid Molecular weight : 36.42 g/mol Describe the procedures and apparatus you need to use for the ...
Saturday, November 22, 2014 at 8:50pm

Chemistry
Which of the following chemical reactions is an example of an endothermic reaction? A. Making ice cubes from liquid water B. Burning a candle C. The evaporation of water D. The combustion of gasoline I think c
Saturday, November 22, 2014 at 7:41pm

chemistry
What is the purpose of a calorimeter? A. To determine the temperature of a chemical reaction B. To determine the energy changes of a chemical reaction C. To identify the specific temperature of an unknown substance I think the answer might be c
Saturday, November 22, 2014 at 7:35pm

Chemistry
Rates of Reactions I am conducting a experiment on increasing the rate of a reaction by increasing the surface area. For this I am reacting hydrochloric acid and marble chips. Variables:- -Independent: the mass of marble chips -Dependent: The volume of gas -Controlled: Temp of...
Saturday, November 22, 2014 at 6:13pm

Chemistry
Rates of Reactions I am conducting a experiment on increasing the rate of a reaction by increasing the surface area. For this I am reacting hydrochloric acid and marble chips. Variables:- -Independent: the mass of marble chips -Dependent: The volume of gas -Controlled: Temp of...
Saturday, November 22, 2014 at 5:09pm

Chemistry
An unknown metal with a mass of 260 g has a heat capacity of 100 J/oC. What is the specific heat of the metal? I am stuck finding the right equation, knowing that the mass is 260 g and heat is 100 J per Celsius. Thus, going with the equation, q=msT, the equation should fit in ...
Saturday, November 22, 2014 at 5:01pm

Chemistry
A volume of 725 mL of a gas is collected at 105 degrees celcius and 746 torr. The gas sample wights 1.92 grams. What is this gas?
Saturday, November 22, 2014 at 4:56pm

chemistry
Which of the following contains more thermal energy? A. Water at 100°C B. Ice at 0°C C. Water at 0°C D. Steam at 100°C I think d
Saturday, November 22, 2014 at 3:53pm

chemistry due soon
Which of the following phrases can describe an endothermic process? A. A system gives off energy as it cools down. B. Energy is released in forming the bonds of the product molecules in a reaction. C. The net energy change for a reaction is positive. D. Energy is transferred ...
Saturday, November 22, 2014 at 3:36pm

Chemistry
It takes 37.16 mL of 0.510 M HCL to neutralize 25.00 mL of NaOh. What is the concentration of the NaOH?
Saturday, November 22, 2014 at 3:33pm

chemistry
I have to calculate the ΔV= final volume-initial volume For the first trial the final volume was .005mL the initial volume was .03mL, which equaled to -.025mL. The volume was negative because it was exothermic reaction. For the second trial the final volume was 0.015 and ...
Saturday, November 22, 2014 at 1:36pm

chemistry Thank a lot help
100ml of h2s04 solution having molarity 1M and density 1.5g/ml is mixed with 400ml of water. Calculate final molarity of h2s04 solution if final density 1.25g/ml. 50ml of 20.8% bacl2 and 100ml of 9.8% h2s04 solution are mixed. Molarity of cl ions in the resulting solution is ...
Saturday, November 22, 2014 at 11:28am

chemistry
A certain reaction is spontaneous at 72˚C. if the enthalpy change for the reaction is 19Kj/mol, what is the minimum value of ΔS (in J/K•mol) for the reaction?
Saturday, November 22, 2014 at 3:18am

chemistry
In a certain experiment a student finds that the PHs of 0.10 M solutions of three potassium salts KX, KY, and KZ are 7.0, 9.0, and 11.0, respectively. Arrange the acids HX, HY, and HZ in order of increasing acid strength.
Saturday, November 22, 2014 at 3:17am

chemistry
In a group 1 analysis, a student adds hydrochloric acid to the unknown solution to make [Cl-] = 0.15 M. Some PbCl2 precipitates. Calculate the concentration of Pb2+ remaining in solutions.
Saturday, November 22, 2014 at 3:14am

Chemistry
Calculate the S(univ) for the following phase change at 25 deg celcius. The boiling point of heptane is 98.0 Celcius and has a Delta Hvap= +21.6kj/mol. C7H16(l)--> C7H16(g) Delta S= +79.0j/k I know that the equation is Delta Suniv= DSsys + DSsurr but for DSurr= -0.216J/371k...
Saturday, November 22, 2014 at 1:06am

Chemistry
If 35.0 mL of 0.210 M HCl reacts with excess Mg, how many mL of hydrogen gas are produced at STP? Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g) Is the answer 2.352 STP converted mols HCl to mols H2 gas: 02.10 M HCl x 1 mol H2/2 mol HCl = 0.105 mol H2 converted mols H2 gas to L: 0...
Saturday, November 22, 2014 at 12:51am

Chemistry
Hf < 0 implies which of the following? A. The temperature decreases B. The temperature remains the same C. A bond-forming process D. A bond-breaking process I think the answer is a.
Saturday, November 22, 2014 at 12:39am

chemistry
If 35.0 mL of 0.210 M HCl reacts with excess Mg, how many mL of hydrogen gas are produced at STP? Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
Friday, November 21, 2014 at 11:45pm

Chemistry
Balance the following equation in basic conditions CoCl2 (s) +Na2O2 (ag) ----> Co(OH)3 (ag)+Cl- (ag) + Na+ (ag)
Friday, November 21, 2014 at 10:56pm

Chemistry
A 3.78 g sample of ethanol (C2H5OH) was burned completely in a bomb calorimeter. The temperature of the calorimeter plus the contents increased from 25.6oC to 35.2oC. Knowing that ethanol's heat of combustion is -3600 kJ/mol, calculate the total heat capacity ( in kJ/oC ).
Friday, November 21, 2014 at 10:35pm

Chemistry
A sample of toluene, C7H8 has a mass of 74.5 g. How many moles of benzene does it contain? How many molecules does the sample contain? How many carbon atoms does it contain?
Friday, November 21, 2014 at 9:46pm

Chemistry
A sample of sodium sulfate, Li2SO4, contains 6.78 x 10^23 formula units. How many moles of Li2SO4 are there in the sample? How many moles of Li+ ions are there in the sample?
Friday, November 21, 2014 at 9:44pm

Chemistry
in a particular redox reaction, MnO2 is oxidized to MnO4– and fe3+ is reduced to fe2+. Complete and balance the equation for this reaction in acidic solution. Phases are optional.
Friday, November 21, 2014 at 5:22pm

Chemistry
when electricity is passed through water, the water decomposes into hydrogen gas and oxygen gas. when 10.00 kg of water were decomposed this way, 5788 l of oxygen gas were produced at 25 degrees celsius and 1 atm pressure. what is the percent yield of oxygen by volume?
Friday, November 21, 2014 at 3:23pm

chemistry
a mixture of 39.8g containing potassium chloride and potassium trioxochlorate (v) upon heating, the residue weighed 28.7g what is the percentage mass of potassium chloride in the residue?
Friday, November 21, 2014 at 1:31am

Chemistry/Physics
When 1mol of a gas burns at constant pressure, it produces 2430J of heat and does 5kJ of work. Calculate change in H, q, and in kJ?
Thursday, November 20, 2014 at 7:30pm

Chemistry/Physics
The kinetic energy of a rolling billiard ball is given by KE=1/2mv2. Suppose a 0.17-kg billiard ball is rolling down a pool table with an initial speed of 4.7m/s . As it travels, it loses some of its energy as heat. The ball slows down to 3.8m/s and then collides straight-on ...
Thursday, November 20, 2014 at 7:27pm

Chemistry
Use bond energy values to estimate delta H fro the following reaction in the gas phase: C2H4 + Br2 -> CH2BrCH2Br I am in dire need of help! Thank you
Thursday, November 20, 2014 at 7:15pm

chemistry
hydrogen gas reacts with oxygen gas to produce water if a student fills a 250-mL flask with hydrogen at STP, what volume of oxygen is necessary for the reaction?
Thursday, November 20, 2014 at 6:58pm

chemistry
One teaspoon of instant coffee ( 3 grams ) is dissolved in 250 grams of water. What percent of the resulting solution is coffee ?
Thursday, November 20, 2014 at 3:31pm

Chemistry
Can you tell if Beer's Law holds for your stock solutions as well as in the calibration range? Why or why not? (P.S. this is a lab question and Beer's Law equation is: A(absorbance) = a(absorptivity) x b(path length) x c(concentration))
Thursday, November 20, 2014 at 2:27pm

Chemistry
If 25.00 mL of 6.00 M HCl is transferred by pipet into a volumetric flask and diluted to 5.00 L, what is the molarity of the diluted HCl? a) 0.75 M b) 0.055 M c) 1.20 x 103 M d) 48.0 M e) 0.0300 M grams of solute/molar mass of solute/liters of solution?
Thursday, November 20, 2014 at 12:56pm

chemistry
what is the partial pressure of hydrogen in a flask containing 2g hydrogen and 32g sulphur dioxide
Thursday, November 20, 2014 at 11:48am

chemistry
The maximum allowable level of nitrate in drinking water set by the state of california is 45mg NO3/l.what is this level expressed in PPm
Thursday, November 20, 2014 at 9:40am

chemistry
If we dissolve 170g sodium acetate in 100g water at 100 degree centigrade , the solution will be saturated or supersaturated
Thursday, November 20, 2014 at 6:23am

Chemistry Numerical
The half life period of a radioactive element is 27.96 days. Calculate the time taken by a given sample to reduce to 1/8th of its initial activity
Thursday, November 20, 2014 at 6:00am

Chemistry
Calculate the time in which the activity of an element is reduced to 90% of its original value. The half-life period of the element is 1.4*10^10 years . Answer :- 2.13*10^9 years
Thursday, November 20, 2014 at 5:58am

chemistry
What voiume of 10.01mol/dm3 commerical H2SO4 is required to prepare 1dm3 of 2mol/dm3 H2SO4 acid solution?
Thursday, November 20, 2014 at 3:33am

chemistry
A 23.9 g piece of metal heated to 97.8 oC is placed in 52.4 g water at 21.9 oC. After the metal is added, the temperature of the water rises to 29.9 oC. Calculate the specific heat of the metal. Express your answer in the units of cal/goC.
Thursday, November 20, 2014 at 1:10am

Chemistry
original question on 11/19 @ 2:26 am current question page 4, close to the bottom.
Thursday, November 20, 2014 at 12:40am

Chemistry
Given a 1.00 M solution of NaOH, describe how you would prepare 500 mL of 0.05 M NaOH solution. You have a 500 mL volumetric flask and a graduated cylinder. I have been trying to figure this question out for over an hour now. I cant seem to place the given numbers into any ...
Thursday, November 20, 2014 at 12:22am

Chemistry
Can you check my answer for the PH question @12:04 11/20?
Thursday, November 20, 2014 at 12:15am

Chemistry
A beaker contains a solution that is 0.50 M in Au+3 ion and 0.25 M in Ag+ ion. A soultion of sodium chloride is slowly dripped into the beaker with stirring. Which ion will precipitate first, the gold or the silver? Clearly support your answer and write out your final ...
Wednesday, November 19, 2014 at 11:57pm

Chemistry
can you look at the additional attached questions from me this morning at 2:29am? not fully understanding them. thanks for your help
Wednesday, November 19, 2014 at 11:25pm

Chemistry
Calculate the molar H3O and ClO3 concentrations of a .28 M solution of perchloric acid (HClO3)?
Wednesday, November 19, 2014 at 10:59pm

Chemistry
Calculate the mass of NH4NO3 salt that should be combined with 100.0 mL of water to obtain a temperature decrease of exactly –15.0C? Delta H of the solution = 24.13 Ccal = 21.12 Csh2o = 4.18 average Qrxn = 1151.6 I dont understand how to solve it
Wednesday, November 19, 2014 at 10:59pm

Chemistry
C2H5NO2 + 2H2O → 2CO2 + NH3 + 3H2 You begin with 1.25 × 10-2 moles of glycine and an excess amount of water that will allow the reaction to proceed completely to products. This is all in a vessel with a volume of 850 mls at 27°C. Assume that the vessel begins ...
Wednesday, November 19, 2014 at 10:32pm

chemistry
Find the percentage of water in Na2CO3*2H2O?
Wednesday, November 19, 2014 at 10:24pm

chemistry
9.03 of Mg combine completely with 3.48g of N to form compound. what is the percent composition of each element in this compound?
Wednesday, November 19, 2014 at 10:23pm

chemistry
29.0g Ag combine completely with 4.30g S to form a compound. what is the percent composition of each element in this compound
Wednesday, November 19, 2014 at 10:20pm

AP chemistry
How do you balance ZnCO3 +O2 yields ZnO + CO2?
Wednesday, November 19, 2014 at 9:32pm

chemistry
An ethylene glycol solution contains 18.2g of ethylene glycol (C2H6O2) in 85.4mL of water. Calculate the freezing point and boiling point of the solution. (Assume a density of 1.00 g/mL for water.)
Wednesday, November 19, 2014 at 8:37pm

chemistry
Calculate the freezing point of a water solution at each concentration. 1.40m? What are the steps to calculate this?
Wednesday, November 19, 2014 at 8:36pm

Chemistry
suppose you added 26.0 ml of 0.01 M NaOH to the solution, what is the molarity of excess NaOH in the mixture? what is the ph of this solution?
Wednesday, November 19, 2014 at 8:29pm

Chemistry: Sigma & Pi bonds
How many sigma bonds and pi bonds are there in each of the following: CH2Cl2 C2H3Cl C5H6 C6N4
Wednesday, November 19, 2014 at 7:07pm

chemistry
10.0 mL of a Cu2+ solution of unknown concentration was placed in a 250 mL Erlenmeyer flask. An excess of KI solution was added. Indicator was added and the solution was diluted with H2O to a total volume of 75 mL. The solution was titrated with 0.20 M Na2S2O3. The equivalence...
Wednesday, November 19, 2014 at 6:49pm

chemistry
What is the molarity of ZnCl2(aq) that forms when 18.0g of zinc completely reacts with CuCl2(aq) according to the following reaction? (Assume a final volume of 165mL .) Zn(s)+CuCl2(aq)→ZnCl2(aq)+Cu(s)
Wednesday, November 19, 2014 at 6:33pm

chemistry
Benzene is a carcinogenic (cancer-causing) compound. A benzene-contaminated water sample contains 3.1×10−5% benzene by mass. What volume of the water in liters contains 225mg of benzene? (Assume that the density of the solution is 1.0 g/mL.)
Wednesday, November 19, 2014 at 6:20pm

chemistry
How many total atoms are in the chemical formula Ai(NO3)3? I thought it was ten because Ai is 1 atom. The No3 is 3 atoms times the 3 is 9 plus the 1 is ten.
Wednesday, November 19, 2014 at 5:24pm

Chemistry
What is the maximum number of orbitals in an atom that can have the following designations? (a) 5p (b) 2pz (c) n=4
Wednesday, November 19, 2014 at 3:35pm

Chemistry
Give the maximum number of electrons in an atom that can have the following set of quantum numbers. (a) n=4 (b) n = 5, ml = 1, (c) n = 5, ms = 1/2
Wednesday, November 19, 2014 at 3:34pm

Chemistry
The ionization energy of Fe is 434 kJ/mol. What is the maximum wavelength of light capable of ionizing Fe? What type of light is this?
Wednesday, November 19, 2014 at 3:33pm

Chemistry
Consider the Li2+ ion. (a) Calculate the wavelength of light emitted when the electron jumps from the n=4 level to the n=2 level. (b) What is the ionization energy of Li2+ ?
Wednesday, November 19, 2014 at 3:32pm

Chemistry
While I3- and Br3- are both stable molecules F3- is not a stable molecule. Provide an explanation.
Wednesday, November 19, 2014 at 3:30pm

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