Tuesday
July 22, 2014

Posts by mad


Total # Posts: 69

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 ?

CHEMISTRY
Sorry these are two different questions

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...

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 ?

CHEMISTRY
NH4+ (aq) + OH- (aq) + energy

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

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 v...

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)

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

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 ene...

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 ) ?

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

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 ?

CHEMISTRY
Yes , added

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

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 ...

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

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

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

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

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

CHEMISTRY
Why can't we use water in electrolytic cell during producing aluminium ?

CHEMISTRY
Why does hydrogen electrode have 0.00 V ? or assumed that has 0.00 V ?

CHEMISTRY
why dry cells are called dry while they contain water ? in electrochemistry

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

CHEMISTRY
But the standard Eo of Cr electrode is -0.74

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

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

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

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

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 befo...

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

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 ??? !!

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

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 ?

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...

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 ,...

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 ...

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

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

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

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

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 ?

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

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

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...

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

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

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

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

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...

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 catal...

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

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

chemistry
I think you want this NaHCO3 + HCl ----> NaCl + H2O + CO2

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

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

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

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 attractio...

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 ?

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^- dec...

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?

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.

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

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

statistics
520

maths
p-mv2\r=mg make m the subject

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

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

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