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October 21, 2014

Homework Help: Science: Chemistry

Recent Homework Questions About Chemistry

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chemistry
2. Calculate the enthalpy change of combustion for ethene gas (C2H4) given the following enthalpy changes of formation: ΔHºf(C2H4)(g) = +52 kJ mol^-1 ΔHºf(CO2)(g) = -394 kJ mol^-1 ΔHºf(H2O)(g) = -286 kJ mol^-1
Saturday, July 19, 2014 at 2:40pm

chemistry
1. Calculate the standard enthalpy change for the reaction: C2H4(g) + H2(g) → C2H6(g) given that the enthalpy of combustion for the reactants and products are: ΔHºc(C2H4)(g) = -1411 kJ mol^-1 ΔHºc(C2H6)(g) = -1560 kJ mol^-1 ΔHºc(H2)(g) = -...
Saturday, July 19, 2014 at 2:40pm

Chemistry
The pH of an acid solution is 5.90. Calculate the Ka for the monoprotic acid. The initial acid concentration is 0.10 M. What I have done: pH = 5.9 a = 10^-5.9 = 1.2589 * 10^-6 Ka = [H+][A-]/[HA] Ka = (1.2589*10^-6)^2/(.01-1.2589) I got -1.26903013E-12, but it's not ...
Saturday, July 19, 2014 at 1:39pm

chemistry step by step for me. Thank a lot
342gm of 20% by mass of ba(oh)2 solution sq gr .57 is reacted with 1200ml of 2m hn03. if the find density is same as pure water then molarity of the ion in resulting solution by nature of the above solution is dentified. The answer 0.888M Who helps me to solve it step step ...
Saturday, July 19, 2014 at 11:24am

chemistry
What is the conjugate acid base in this equation: h2so4+h20---Hso4^-+h3o^+ 2:) which phase of matter can act as a solvent. A.gas B.solid C.liquid D.all the above
Friday, July 18, 2014 at 10:08pm

chemistry
For the number 2 question. It is asking. How mnay ML of solute will be dissolved in a 435 ML of 5.4%V/V of HCI solutions.
Friday, July 18, 2014 at 8:19pm

chemistry
So i if do 4 x250/100 i will get the answer for the prob?
Friday, July 18, 2014 at 7:40pm

chemistry
What mass of solute is dissolved in 250.ml of 4.00%m/v solution. I am confused what to do.in response to question 2 of my other question it asking for volume of the solute.
Friday, July 18, 2014 at 6:51pm

chemistry
What will be the molarity of 335 ml of solutions containing 1.02 g of magnesium perchlorate. Here what i think divide 335/1.02 to get answer but i am not sure. Question 2:) how many ml of solute will be dissolved in a 435ml of 5.4%v/v of hci solution. I am thinking divide ...
Friday, July 18, 2014 at 6:10pm

chemistry
I got kc to be 0 but that has got be wrong
Friday, July 18, 2014 at 4:46pm

chemistry
A mixture of 0.100 mol NO, 0.200 mol H2 and 0.0800 mol N2 were placed in a 2.00L reaction vessel, heated, and allowed to come to equilibrium conditions. At equilibrium, the molar concentration of N2 was 0.0500 mol/L. Calculate Kc for this reaction. 2NO + 2H2 <---> N2 + ...
Friday, July 18, 2014 at 4:37pm

chemistry
how to find a structure factor of a face centerd cubic lattice
Friday, July 18, 2014 at 12:33pm

chemistry
The weight of one atom of uranium is 238amu.its actual weight is
Friday, July 18, 2014 at 6:14am

Chemistry
What quantity of heat is required to convert 200g of ice at 0.00C into water at 50C? I know that im suppose to use the E=mc(Delta T) but im not sure how...
Thursday, July 17, 2014 at 6:41pm

Chemistry
What quantity of heat (kJ) is required to convert 200g of ice at 0.00C into water at 50C?
Thursday, July 17, 2014 at 6:29am

Chemistry
I got 0.907 KJ for ΔHcomb but I don't know if its correct. I also don't know how to write the equation. -------- question: A calorimeter is filled with 10.0 mole of methane gas and an excess of oxygen. When burned, the ignition wire releases 107.2 J of heat. The ...
Wednesday, July 16, 2014 at 11:39pm

chemistry
When 3.00 moles of sodium are reacted with large amounts of chlorine gas 145.8 g of sodium chloride are produced determine percentage yield
Wednesday, July 16, 2014 at 10:51pm

Chemistry
I got 0.907 KJ for ΔHcomb but I don't know if its correct. I also don't know how to write the equation. -------- question: A calorimeter is filled with 10.0 mole of methane gas and an excess of oxygen. When burned, the ignition wire releases 107.2 J of heat. The ...
Wednesday, July 16, 2014 at 9:02pm

Chemistry
An aqueous solution of NaCl is 270m. If the density of the solution is 1.20g/ml. Find a) % NaCl by mass b) Molarity of NaCl in the solution.
Wednesday, July 16, 2014 at 9:53am

CHEMISTRY
HF + H2O <==> H3O+ + F- By dissolving 0.03 mol HF in 1 L water , seen that [HF] at the equilibrium is 0.027 M , then : 1) If we divide 0.03 mol/ 1 L it would be 0.03 M , why that difference ? 2) How many moles HF in 1 L water is required to reach the equilibrium ?
Wednesday, July 16, 2014 at 7:57am

CHEMISTRY
I have trouble how to resist pH in buffer solutions ( in acidic buffer , and in basic buffer ) when we add an acid , and a base ! how the reactions in buffer follow Le chatlier's principle ?
Wednesday, July 16, 2014 at 7:33am

chemistry
275 ml of active ingredient is added to 725 ml of an alcohol based solution. What is the final strength (v/v)
Tuesday, July 15, 2014 at 7:23pm

Chemistry
Determine the pH of the following solutions: a) A 250.0 mL solution that contains 0.125 M benzoic acid and 0.147 M sodium benzoate. b) The solution in part (a) after 30.0 mL of 0.510 M hydrochloric acid has been added. a. Ka = 6.3 x 10^-5 pKa = 4.20 pH = pKa+log(base/acid) pH...
Tuesday, July 15, 2014 at 6:30pm

Chemistry
1. A solution is prepared such that it is 0.45 M in formic acid and 0.35 M in sodium formate. a) Where is this mixture located on a titration curve: before the buffer point, at the buffer point, or after the buffer point? b) Use the Henderson-Hasselbach to determine the pH of ...
Tuesday, July 15, 2014 at 4:59pm

Chemistry
Benzene reacts with hot concentrated nitric acid dissolved in sulfuric acid to give chiefly nitrobenzene, C6H5NO2. A by-product is often obtained, which consists of 42.86% C, 2.40% H, and 16.67% N (by mass). The boiling point of a solution of 5.5 g of the by-product in 45 g of...
Tuesday, July 15, 2014 at 11:45am

Chemistry
A saturated solution is made by dissolving 0.252 g of a polypeptide (a substance formed by joining together in a chainlike fashion some number of amino acids) in water to give 1.92 L of solution. The solution has an osmotic pressure of 3.69 torr at 25 °C. What is the ...
Tuesday, July 15, 2014 at 11:37am

Chemistry
Glauber's salt undergoes a phase transition according to the following equation: Na2SO4*10H2O(s)--> Na2SO4*10H2O(l) ∆H = 74.4 kJ/mol Calculate the mass (g) of Glauber's salt (use the masses to two decimal places found in the front of your text) needed to lower...
Tuesday, July 15, 2014 at 9:05am

Chemistry
A solution of acetic acid was prepared by mixing glacial acetic acid with water.The solution was 25% of acetic acid by volume.How much glacial axetic acid must be used to prepare 120 mL of desired volume?
Tuesday, July 15, 2014 at 8:54am

Chemistry
How much ethanol must be used to prepared 150 mL 10% by volume?
Tuesday, July 15, 2014 at 8:52am

chemistry
The concentration of vinegar was obtained by titration. 20 ml of vinegar required 43.2 ml of 0.350 M sodium hydroxide. Find the concentration of vinegar
Tuesday, July 15, 2014 at 7:21am

chemistry
A certain sample of gas has a volume of 500 ml. at a pressure of 1.5 atmosphere.What will be its volume if the gas is submerged toa pressure of 5 atmosphere at constant temperature?
Tuesday, July 15, 2014 at 2:39am

chemistry
How would polyethylene have the VSEPR shape of tetrahedral?
Monday, July 14, 2014 at 11:16pm

Chemistry
A 38.9 g piece of iron at 84.6oC is placed in a beaker containing 179.7 g of 20.7oC water. What is the final temperature (oC)of the water?
Monday, July 14, 2014 at 9:50pm

Chemistry
. An equal mass of which of the following states of matter could completely fill both a 100 mL or 500 ml container? A. Gas B. Liquid C. Mixture D. Solid
Monday, July 14, 2014 at 9:35pm

chemistry
How much 9% solution can you make by diluting 350ml of a 15% solution?
Monday, July 14, 2014 at 8:33pm

Chemistry
An unknown metal with a mass of 313 g has a heat capacity of 121 J/oC. What is the specific heat of the metal?
Monday, July 14, 2014 at 7:48pm

Chemistry
Although I do very well in chemistry I never really understood converting units. Perform each of the following conversions. A. 8.43cm to millimeters B. 2.41x10^2cm to meters C. 294.5nm to cm D. 1.445x10^4m to kilometers E. 235.3m to millimeters F. 903.3nm to micrometers
Monday, July 14, 2014 at 3:15pm

Chemistry
A saturated solution is made by dissolving 0.325 g of a polypeptide (a substance formed by joining together in a chainlike fashion some number of amino acids) in water to give 1.37 L of solution. The solution has an osmotic pressure of 4.13 torr at 28 °C. What is the ...
Monday, July 14, 2014 at 1:50pm

Chemistry
Benzene reacts with hot concentrated nitric acid dissolved in sulfuric acid to give chiefly nitrobenzene, C6H5NO2. A by-product is often obtained, which consists of 42.86% C, 2.40% H, and 16.67% N (by mass). The boiling point of a solution of 5.5 g of the by-product in 45 g of...
Monday, July 14, 2014 at 1:49pm

Chemistry
At 21.0 °C, a solution of 23.71 g of a nonvolatile, nonpolar compound in 30.64 g of ethylbromide, C2H5Br, had a vapor pressure of 319.7 torr. The vapor pressure of pure ethyl bromide at this temperature is 400.0 torr. Assuming an ideal solution, what is the molecular mass ...
Monday, July 14, 2014 at 1:49pm

Chemistry
A solution of acetic acid, CH3COOH, has a concentration of 0.218 M and a density of 1.00 g mL-1. What is the molality of this solution?
Monday, July 14, 2014 at 1:48pm

CHEMISTRY
NH3(g) + H2O(l) <==> NH4+ (aq) + OH- (aq) a) According to delta H ( Enthalpy ) , which direction the equation will shift ? b) According to Entropy , which direction the equation will shift ? c) Assuming that delta G is positive , then delta S is greater than delta H or ...
Monday, July 14, 2014 at 10:01am

CHEMISTRY
Determine that which directions ( left or right ) shift , of these following equations according to the Entropy 1) HCl (l) <==> HCl (g) 2) C6H12O6 (aq) <==> C6H12O6 (s) 3) 2NH3 (g) <==> N2(g) + 3H2(g) 4) 3C2h$(g) <==> C6H12 (l)
Monday, July 14, 2014 at 9:12am

CHEMISTRY
If heat of combustion of acetylene C2H2 is -1301.1 kJ/mol then : a) Write balanced thermochemical equation of acetylene combustion b) If 0.25 mol C2H2 reacted according to the previous equation , and what is the emitted energy ? c) how many grams needed to give off 3900 kJ ...
Monday, July 14, 2014 at 9:05am

chemistry
A sample of solid ammonium chloride, NH4Cl, is dissolved in water. The solution formed was found to be acidic. Can you please explain why the solution is acidic?
Monday, July 14, 2014 at 6:24am

CHEMISTRY
We have this reaction : HCO3- + OH- => CO3^-2 + H2O Specify the conjugate pairs and , which direction the reaction equilibrium shift ? and How ( as a rule ) ?
Monday, July 14, 2014 at 5:23am

CHEMISTRY
We have : Cl | 1) :B-Cl with two unshared electrons | Cl F | 2) :N-F | F then , if we assume that N and B bind covalently , which of them is acid ? And is that also bronshted- lowry acid ? explain thanks
Monday, July 14, 2014 at 4:51am

CHEMISTRY
Which of the following solutions do they have the maximum osmotic pressure : 1) 0.1 m ( molal conc.) glucose 2) 0.1 m sucrose 3) 0.5 m glucose 4) 0.2 m sucrose and why ?
Monday, July 14, 2014 at 4:31am

Chemistry
In the titration of an acid, how do you know when to stop adding the standardized base?
Sunday, July 13, 2014 at 7:35pm

Chemistry
The concentration of glucose in blood is 5.67%m/v. How many grams of glucose would be found in an adult male with a blood volume of 5.2L?
Sunday, July 13, 2014 at 7:35pm

Chemistry
At the instant that an elastic falling object strikes the ground and becomes compressed, which of the following energy transformations occurs? A. Gravitational to electric B. Potential to kinetic C. Electric to gravitational D. Kinetic to potential I think it is D.
Sunday, July 13, 2014 at 5:10pm

Chemistry
Three liquids of differing densities are studied. Samples of liquid 1 and liquid 2 are placed in a container together. Liquid 1 rises to the top. Another sample of liquid 1 is placed in a different container together with liquid 3. This time, liquid 3 rises to the top. If all ...
Sunday, July 13, 2014 at 3:09pm

Chemistry
Determine the density of methane (CH4) in g/L at 27.8oC and 1.1 atm.
Sunday, July 13, 2014 at 2:09pm

Chemistry
A volume of 0.155 L of a gas at STP weighs 0.412 g. Calculate the molar mass of the gas.
Sunday, July 13, 2014 at 2:08pm

Chemistry
NaOH + HS0-+ Hp + NaS0 24 24 Which of the following is the number of moles of NaOH required to neutralize 1 mole of H2S04 in the equation above? (Note: The reaction is not balanced.) A. 0.5 moles B. 1 mole C. 1.5 moles D. 2 moles 1
Sunday, July 13, 2014 at 11:50am

chemistry
. A student wants to design an experiment to demonstrate the effects of acid rain on plant life. Which of the following substances should be combined with water to best simulate acid rain? A. Vinegar B. Table salt C. Baking soda D. Ammonia
Sunday, July 13, 2014 at 11:40am

Chemistry step by step thank a lot
10L of hard water required 5.6g of lime for removing hardness. Hence temporary hardness in ppm of cac03 The answer 1000 Who helps me to solve it for me step by step clearly Thank a lot all tutors
Sunday, July 13, 2014 at 11:27am

chemistry
A certain reaction has an activation energy of 25.14 kJ/mol. At what Kelvin temperature will the reaction proceed 8.00 times faster than it did at 305 K?
Sunday, July 13, 2014 at 11:12am

chemistry
Consider the following mechanism. Step1: A+B<---->c (equilibrium) Step 2: C+A---->d (slow). Overall: 2A+B---->D. Determine the rate law for the overall reaction (where the overall rate constant is represented as k).
Sunday, July 13, 2014 at 10:39am

chemistry
Consider the following mechanism. Step1: 2A--->B (SLOW) Step2: B+C--->D (fast) Overaall: 2A+C--> D Determine the rate law for the overall reaction (where the overall rate constant is represented as k).
Sunday, July 13, 2014 at 10:36am

chemistry
The activation energy for a particular reaction is Ea = 14.80 kJ. What percentage of the molecules are at or above the activation energy at 500.0 K?
Sunday, July 13, 2014 at 10:32am

chemistry step bystep thank a lot
10L of hard water required 5.6g of line for removing hardness. Hence temporary hardness in ppm of cac03. The answer 1000 ppm= 1mg/1L cac03 = 100 g/mol who solve it for me clearly step by step Thank a lot all tutors
Saturday, July 12, 2014 at 9:44pm

chemistry step by step for me clearly
Al2(s04)3 solution of a molal concentration is present in 1 litre solution of 2.684g/cc. How many moles of bas04 would be precipitated on adding bacl2 in excess. The answer 6M I want some tutors to explain for me step by step clearly. I do not still understand Thank a lot all ...
Saturday, July 12, 2014 at 10:36am

CHEMISTRY
The solubility of KClO3 in 25 oC is 10 g solute per 100 g water if 15 g of KClO3 is embedded in 100 g water in 25 oC , then , what is the amount of KClO3 that can be dissolved ? is the solution unsaturated , saturated , or super saturated ? thank you
Saturday, July 12, 2014 at 7:51am

CHEMISTRY
Dye of iodine is prepared by dissolving in ethanol , and 1% ( one percent ) of this solution contains 10 g of solute in 1000 g of solution 1) how many grams of solvent is there in the solution ? 2) how many moles of solute ( I2) is there? 3) what is the molality of 1% of this ...
Saturday, July 12, 2014 at 7:46am

chemistry step by step thank a lot
Al2(s04)3 solution of a molal concentration is present in 1 litre solution of 2.684g/cc. How many moles of bas04 would be precipitated on adding bacl2 in excess? the answer 6M Who helps me step by step for me clearly I am thankful to all tutors
Friday, July 11, 2014 at 11:25pm

chemistry
explain whether using solid sodium hydroxide pellets rather than aqueous sodium hydroxide would alter the enthalpy
Friday, July 11, 2014 at 10:12pm

Soil Chemistry
how is carbon dioxide different than water in terms of the behavior of each compound in Earth's atmosphere?
Friday, July 11, 2014 at 8:39pm

Chemistry
Write an equation for the reaction that takes place when each base is added to water. A) LiOH B) (CH3)2NH.
Friday, July 11, 2014 at 6:19pm

chemistry
Why would you have to subtract the heat capacity of the calorimeter when calculating the heat of the reaction?
Friday, July 11, 2014 at 5:21pm

chemistry
what mass of ethanol could form from fermentation of 90.0g of glucose? what is the percentage yield if 6.0g of ethanol forms?
Friday, July 11, 2014 at 3:39pm

chemistry
Why would you have to subtract the heat capacity of the calorimeter when calculating the heat of the reaction?
Friday, July 11, 2014 at 2:16pm

chemistry
calculatethe volume of o2 and volume of al needed photon combusion on 18 kg at carbon
Friday, July 11, 2014 at 12:05pm

chemistry
calculate the volume of o2 and volume al needs photon combison on 18 kg at carbon
Friday, July 11, 2014 at 11:58am

chemistry
We can build the model in a spreadsheet simulating ten layers in the filter. For each layer we calculate the headloss with Carmen-Kozeny and calculate from this the pressures as a function of the place in the filter. Calculate the headloss and the actual pressure in each layer...
Friday, July 11, 2014 at 6:40am

Chemistry
You are a work study student in our chemistry department. Amy, your supervisor has just asked you to prepare 250ml of 2.00M H2SO4 solution for tomorrow's undergraduate experiment. The Stock Solutions cabinet is under the Stockroom Explorer. You will find find a 2.50 liter ...
Thursday, July 10, 2014 at 9:12pm

chemistry
a block of metal has a volume of 13.4in^3 and a weight of 5.14 lb. what is its density in grams per cm^3? Show operation
Thursday, July 10, 2014 at 8:41am

CHEMISTRY
Is these two electrodes appropriate to create a good battery ? : Cd => Cd^+2 + 2e- and Fe => Fe^+2 + 2e- Explain
Thursday, July 10, 2014 at 8:19am

CHEMISTRY
If a nickel rod embedded in a silver nitrate solution , what do we predict ? explain
Thursday, July 10, 2014 at 8:09am

CHEMISTRY
Assuming that this half cell I2 + 2e- + =>2I- as standard electrode and assumed its potential that is 0.00 V : a) what is standard potential of this half cell : Br2 + 2e- + => 2Br- b) what is standard potential of this half cell : Al^+3 + 3e- => Al
Thursday, July 10, 2014 at 7:57am

CHEMISTRY
Can a substance made of zinc be coated by nickel , using nickel nitrate solution ? How ?
Thursday, July 10, 2014 at 6:42am

CHEMISTRY
In electrolysis , which reaction does occur on the cathode , half oxidation reaction or reduction ?
Thursday, July 10, 2014 at 6:32am

CHEMISTRY
Why can't we use water in electrolytic cell during producing aluminium ?
Thursday, July 10, 2014 at 6:23am

CHEMISTRY
Why does hydrogen electrode have 0.00 V ? or assumed that has 0.00 V ?
Thursday, July 10, 2014 at 6:14am

CHEMISTRY
why dry cells are called dry while they contain water ? in electrochemistry
Thursday, July 10, 2014 at 6:08am

CHEMISTRY
The standard potential of this cell Sn|Sn^+2 || Cr^+3|Cr is -0.60 V , what is the reductional standard potential of Cr^+3|Cr ? if we know that reduction potential of Sn is Sn^+2 + 2e- <==> Sn : -0.14 V
Thursday, July 10, 2014 at 5:38am

chemistry
how to find which is quantum number and magnetic quantum number
Thursday, July 10, 2014 at 4:22am

Chemistry
A mixture of ammonia and oxygen is prepared by combining 0.250 L of NH3 (measured at 0.700 atm and 20°C) with 0.160 L of O2 (measured at 0.720 atm and 49°C). How many milliliters of N2 (measured at 0.740 atm and 100. °C) could be formed if the following reaction ...
Wednesday, July 9, 2014 at 4:26pm

Chemistry
Methane is formed in landfills by the action of certain bacteria on buried organic matter. If a sample of methane collected from a landfill has a volume of 200. mL at 741 torr and 27.2 °C, how many grams of methane are in the sample? I get the PV=nRT p is 741/760= .975 V ...
Wednesday, July 9, 2014 at 3:43pm

Chemistry
How much ethylene glycol (C2H6O2, the major component of antifreeze) must be added to 1 L of water to keep from it freezing at -15 °F?
Wednesday, July 9, 2014 at 10:37am

CHEMISTRY
What is the function ( or role ) of platinum in electrochemistry in general ? I read a question about platinum in electric potential , and in standard electrode potential ?! thank you a lot
Wednesday, July 9, 2014 at 9:37am

CHEMISTRY
How many oxidation states Should a substance have at least to undergo Disproportionation reaction ? thanks
Wednesday, July 9, 2014 at 9:31am

CHEMISTRY
A substance contains an element at its probable maximum oxidation number , does this substance have a maximum chance to be an oxidizing agent or have a minimum chance to be a reducing agent ? thank you
Wednesday, July 9, 2014 at 9:26am

CHEMISTRY
I have trouble finding out the oxidation number of each element in the : [Cr(N2h4CO)6]4[Cr(CN)6]3
Wednesday, July 9, 2014 at 5:58am

CHEMISTRY
I have these equations in our book , but I've tried a few times to solve it in half reaction method , but I couldn't yet : 1) KMnO4 + KIO3 => MnO2 + KIO4 ( in a basic solution ) 2) MnO4- + Cl- => Mn^+2 + HClO ( in a acidic solution ) I think these are incorrect...
Wednesday, July 9, 2014 at 5:56am

chemistry
FIND THE PERCENTAGE BY VOLUME COMPOSITION OF A VINEGAR SOLUTION CONTAINING 10cm (TO THE POWER OF 3) OF ACETIC ACID AND 190 (TO THE POWER OF 3)OF H2O
Wednesday, July 9, 2014 at 4:40am

chemistry
if you need 50.0 grams of lead2 chloride how much magnesium chloride would you need?
Wednesday, July 9, 2014 at 12:34am

chemistry
What is the mass of water obtained when mix 100.0 mL of 2.5 M. HNO3 with 100.0 mL of 2.55 M. KOH?
Tuesday, July 8, 2014 at 8:49pm

CHEMISTRY
Balance the oxidation reduction equation in half reaction PbO2 + KCl => KClO + KPb(OH)3 thank you a lot
Tuesday, July 8, 2014 at 2:25pm

Chemistry
How many milliliters of O2 are consumed in the complete combustion of a sample of hexane, C6H14, if the reaction produces 325 mL of CO2? Assume all gas volumes are measured at the same temperature and pressure. The reaction is 2C6H14(g) + 19O2(g) -> 12CO2(g) + 14H2O(g)
Tuesday, July 8, 2014 at 12:50pm

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