Wednesday
September 17, 2014

Posts by mad


Total # Posts: 74

CHEMISTRY
How do the indicators work , by changing color ?
September 12, 2014

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 )
September 12, 2014

CHEMISTRY
What is difference between equivalence point and end point in the titration ?
September 11, 2014

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 - ...
September 11, 2014

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

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

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 ?
July 16, 2014

CHEMISTRY
Sorry these are two different questions
July 16, 2014

CHEMISTRY
CO3^-2 + H3O+ <==> HCO3- + H2O and HPO4^-2 + H2O <==> OH- + H2PO4- During the increasing of the forward reaction , the pH of the solutions would be : 1) increased 2) decreased 3) the same 4) may be increased or decreased My question is that which of them is correct...
July 16, 2014

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 ?
July 16, 2014

CHEMISTRY
NH4+ (aq) + OH- (aq) + energy
July 14, 2014

CHEMISTRY
Sorry NH3(g) + H2O(l) <==> NH4+ (aq) + OH- (aq) + energy
July 14, 2014

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 ...
July 14, 2014

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)
July 14, 2014

CHEMISTRY
I think it's so : a) 2C2H2 + 5O2 => 4CO2 + 2H2O + 1301.1kJ b) 0.25mol * 1301.1 kJ = 325.27 kJ energy released c) 1301.1 kJ/1mol = 3900 kJ/ x mol = 2.99mol then X g = mol * molar mass of C2H2 X g = 2.99mol * 26 g/mol = 77.74 g
July 14, 2014

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 ...
July 14, 2014

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 ) ?
July 14, 2014

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
July 14, 2014

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 ?
July 14, 2014

CHEMISTRY
Yes , added
July 12, 2014

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
July 12, 2014

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 ...
July 12, 2014

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

CHEMISTRY
If a nickel rod embedded in a silver nitrate solution , what do we predict ? explain
July 10, 2014

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
July 10, 2014

CHEMISTRY
Can a substance made of zinc be coated by nickel , using nickel nitrate solution ? How ?
July 10, 2014

CHEMISTRY
In electrolysis , which reaction does occur on the cathode , half oxidation reaction or reduction ?
July 10, 2014

CHEMISTRY
Why can't we use water in electrolytic cell during producing aluminium ?
July 10, 2014

CHEMISTRY
Why does hydrogen electrode have 0.00 V ? or assumed that has 0.00 V ?
July 10, 2014

CHEMISTRY
why dry cells are called dry while they contain water ? in electrochemistry
July 10, 2014

CHEMISTRY
Of course it's not a made up problem , it's only a question in our homework Sometimes , I'm just confused on some fine and tiny problems , just it is.. I'm sorry for any mistake and , I'm very grateful
July 10, 2014

CHEMISTRY
But the standard Eo of Cr electrode is -0.74
July 10, 2014

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
July 10, 2014

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
July 9, 2014

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

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
July 9, 2014

CHEMISTRY
Not only I don't think so , but I believe it's impossible to balance that , but there is no such reaction and such authentic and valid rxn and equation ! because how possible in chemistry science world that there be an substance has two different oxidation numbers ...
July 9, 2014

CHEMISTRY
Ok , I really thank you , but if it's so , can we balance this equation in half reaction method ? : [Cr(N2H4CO)6]4[Cr(CN)6]3 + KMnO4 + H2SO4 ---> K2Cr2O7 + MnSO4 + CO2 + KNO3 +K2SO4 + H2O
July 9, 2014

CHEMISTRY
So , on the reactant site you assigned two Chrome in two different oxidation number , but really and basically , is such something possible ? how is it possible one element in a compound on a site of reactant or products has two different oxidation number ??? !!
July 9, 2014

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

CHEMISTRY
Oh ! that was only wrong of typing So it's not wrong with having a "mixed" equation in which you have both molecules and ions ?
July 9, 2014

CHEMISTRY
Yes , 3IO3- + 6OH- => 3IO4- + 6e- + 3H2O 2MnO4- + 6e- + 4H2O => 2MnO2 + 8OH- ___________________________________ + 3IO3 + 2MnO4- + H2O => 3IO4- + 2MnO2 + 2OH- and , the final balanced equation is : 3KIO3 + 2KMnO4 H2O => #KIO4 + 2MnO2 + 2OH- so , is it possible that...
July 9, 2014

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...
July 9, 2014

CHEMISTRY
But ? but in the main reaction , the ClO^- is on the product site not reactant , as you put it on the reactant site , I mean Cl- is oxidized to ClO^- ! On the other hand , I can balance it by myself , but I'm having trouble with KPb(OH)3 , I don't know how to separate ...
July 8, 2014

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

CHEMISTRY
But there are other sources that gave -1 to H in N2H4 abd +2 to N !
July 8, 2014

CHEMISTRY
But it is -1 when bonded with a non metal (N) , and it's also -1 when bonded with a metal ( Ca )
July 8, 2014

CHEMISTRY
Why the oxidation number of ( H ) is -1 in 1) N2H4 2) CaH2 while ( N ) is different from ( Ca ) ?
July 8, 2014

CHEMISTRY
In half reaction method of the chemical equation balancing , how about those redox reactions that they don't contain any (H) and ( O ) atoms ?
July 8, 2014

CHEMISTRY
In relative oxidizing and reducing agents table ; 1) Is Al oxidized by Ni+2 2) Is Cu oxidized by Ag+ 3) Is Pb oxidized by Na+ 4) Is F2 reduced by Cl- 5) Is Br2 reduced by Cl- and if you or no , how it is as a rule to predict any ? thank you
July 8, 2014

CHEMISTRY
Assume that the ( S ) ( S ; alphabet ) is the solubility in mol/L of AB2 compound , , then what is the concentration of A and B ? and what is the Ksp of AB2 compound ? thank you a lot
July 8, 2014

CHEMISTRY
The Ksp of (hydroxyapatite ) Ca5(PO4)3OH is 6.8 * 10^-37 , and its molar concentration is 2.7 * 10^-5 mol/L ,, if this (hydroxyapatite) reacts with fluoride , then the F- ions replace OH- ions and the product is Ca5(PO4)3F ,, if we know the Ksp of ( fluoroapatite ) is 1.0 * 10...
July 8, 2014

chemistry
Why did you use 160 instead of 2.48 g ? and , how do I know #1 and #3 is endothermic and #2 is exothermic ? thank you
July 7, 2014

CHEMISTRY
Does it produce precipitate if 1.7 g of AgNO3 and 14.5 g of NaCl solvated in 200 mL water to get a solution in 25 oC ? thank you
July 7, 2014

CHEMISTRY
If 2.5 * 10^-2 g of Fe(NO3)3 added to 100mL of 1.0 * 10^-4 M NaOH solution , will it produce precipitate ? thank you
July 7, 2014

CHEMISTRY
I'm sorry the underlines are " 1) CO2 2) [ Cu(NH3)4 ]^+2 3) I2 4) 2Cl2 5) Cl2
July 7, 2014

CHEMISTRY
Which conditions ( reactant concentration , pressure , and temperature ) elevate high concentration of the underlines in these following equilibrium systems : 1) 2CO + O2 <==> 2CO2 + 167 kJ 2) Cu^+2 + 4NH3 <==> [ Cu(NH3)4 ]^+2 + 24 kJ 3) 2HI + 12.6 kJ <==> H2...
July 7, 2014

CHEMISTRY
We have this following gas equilibrium : H2 + Cl2 <==> 2HCl + 184 kJ then predict the following to know Le chatlier's prediction 1) adding Cl2 2) removing HCl 3) elevation of pressure 4) lowering of the temperature 5) removing H2 and lowering pressure 6) adding ...
July 7, 2014

CHEMISTRY
The enthalpy change of an endothermic reaction is 8 kJ , and this reaction is spontaneous at 25 oC ,, what is the expected entropy change ? thank you a lot
July 6, 2014

CHEMISTRY
Find the specific heat of indium , if any one mole absorbs 23 J , when the temperature elevates from 297.5 K to 299.5 K thank you so much
July 6, 2014

chemistry
I think you want this NaHCO3 + HCl ----> NaCl + H2O + CO2
July 6, 2014

CHEMISTRY
Which of the following is the conjugate acid to a base in these options : 1) PO4^-3 2) H2O 3) H3PO4 4) H2PO4^-
July 4, 2014

CHEMISTRY
Which of the following is the conjugate acid to a base in these options : 1) PO4^-3 2) H2O 3) H3PO4 4) H2PO4^-
July 4, 2014

CHEMISTRY
Which of the following pairs are conjugate pairs ? 1) H+ and OH- 2) HCl and Cl- 3) NH2- and NH4+ 4) H2SO4 and SO4^-2 thanks a lot
July 4, 2014

CHEMISTRY
A) We have an experiment , using the solution of KNO3 , measured freezing point of solution is -1.15 degree , and using a sample of pure water the thermometer read o.25 degree as freezing point of the sample , calculate the molal concentration of KNO3 assume that the ...
July 4, 2014

CHEMISTRY
The solubility of a substance is 12 g per 100 g water at 20 degree , and is 18 g per 100 g water at 60 degree , what is the mass of the substance can be crystallized in a saturated solution that contain 200 g of water , if the solution cooled from 60 to 20 degree ?
July 3, 2014

Chem
given the reaction: agcl(s) +2nh3 (aq) <--> ag (nh3)2 +(aq) + cl^- (aq). if more ammonia, nh3 is added to the system at equilibrium the a) amount of agcl increases b) system cannot achieve equilibrium c) rate of the forward reaction decreases d) concentration of cl^- ...
June 3, 2013

Chem
consider the equilibrium reaction: pbcro4(s) <--> pb^2+ (aq) +cro4^2- (aq). A saturated solution of lead chromate, pbcro4 has a lead ion concentration of 1.4 x 10^-7 m. what is the value of the solubility product ksp for lead chromate?
June 3, 2013

math
The volume V of a pyramid varies jointly as the area of the 1. ________________________ base B and the height h, and V=24 ft3 when B=12 ft2 and h=6ft. Find B when V=54 ft3 and h=9 ft.
April 28, 2013

Chemistry
D is not conjugate pairs , because the anion part of the acid ( NO3 - of HNO3 ) differs from the NO2-
March 10, 2013

Chemistry
what is the molality of a solution prepared by dissolving 13.0 g of Ba(NO3)2 in 450 g of water?
April 17, 2012

statistics
520
December 15, 2011

maths
p-mv2\r=mg make m the subject
November 10, 2009

Math - 3rd grade
I am so stupid, I cant even answer this question!
January 7, 2008

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