MAD

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 2...

11 years ago

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 ass...

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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)...

11 years ago

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 <==...

11 years ago

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

11 years ago

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

11 years ago

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 ( fluor...

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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 inc...

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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 m...

11 years ago

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

11 years ago

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 ?

11 years ago

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

11 years ago

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 ) ?

11 years ago

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 t...

11 years ago

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)

11 years ago

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 t...

11 years ago

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 ?

11 years ago

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 equi...

11 years ago

Classify these mixtures to homogeneous and heterogeneous a) orange juice b) tap water ( home water )

11 years ago

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

11 years ago

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) ph...

11 years ago

What is difference between equivalence point and end point in the titration ?

11 years ago

How can we determine the equivalence point ( or end point ) in the curves in titration ( strong acid/weak base and weak acid/strong base )

11 years ago

How do the indicators work , by changing color ?

11 years ago

What is the molality of 22.5 g acetone (CH3)2CO , in 200 g water ? ( the answer is 22.0 m , that I think is wrong .. )

11 years ago

Why dissolving gases in the liquids is exothermic while the phase is down ? explain please

11 years ago

The solubility of LiCl is 83.5 g/100 g H2O at 20 oC , and is 89.8 g / 100 g H2O at 40 oC , then what is the required mass (in gram ) of LiCl to obtain a saturated solution in 300 g H2O at 25 oC ? please explain thank a lot

11 years ago

The solubility of NaNO3 at 40 oC is 102 g/100 g H2O , what is the minimum amount of water to dissolve NaNO3 ( mass of solvent ) ?

11 years ago

Which solute will yield a saturated solution ( in the previous two question ) when we dissolve 36 g of each in 25 g of water at 25 oC ? and why ?

11 years ago

Does a molecular compound in water have hydration or have ionization ?

11 years ago

I can't understand rounding rules of numbers Can you simply explain it ?

10 years ago

If we have : H2(g) + 1/2 O2(g) -> H2O(l) dHf= -285.5 Kj N2O5(g) + H2O(l) -> 2HNO3 dHf = -76.6 Kj 1/2 N2 + 3/2 O2 + 1/2 H2 -> HNO3 dHf = - 174.1 Kj then , what is the dHf of 2N2 + 5O2 -> 2N2O5

10 years ago

Are there any tips to help to learn and memorizing the phrasal verbs in english ? With Respects

10 years ago

I want to write a CV , could you help and notice me how to do it ? with respects

10 years ago

A person hammered a 0.5 kg something (substance ) with a hammer that its weight is 2.5 kg , with the velocity 65 m /s ,, if one third of the hammer's energy turn into the internal energy to both of the substance and the hammer , then what is the change (i...

10 years ago

A piece of ice its mass is 2.5 kg and at 0.0 C temperature , it is crawling on the ground with 5.7 m/s , what is the mass of the melted ice , if we know all of the kinetic energy of the ice turn into the internal energy (of the ice ) , that we need 3.3 X...

10 years ago

What is basically difference between the following : 1)Internal energy and latent heat 2)Internal energy and potential energy I'm really confused , because they're so close in meaning. Thanks

10 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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 ho...

11 years ago

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...

11 years ago

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 pos...

11 years ago

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

11 years ago

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 ?

11 years ago

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 oxidatio...

11 years ago

But the standard Eo of Cr electrode is -0.74

11 years ago

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

11 years ago

Yes , added

11 years ago

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

11 years ago

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

11 years ago

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

11 years ago

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...

11 years ago

Sorry these are two different questions

11 years ago

but 22.5/58 = 0.3879 , and 0.3879/0.2 = 1.9 but the answer is another (22) .. I can't get it

11 years ago

I mean the phase of the gas is going towards being liquid

11 years ago

Please

11 years ago

Please

11 years ago

I'm confused , can you do the solution please ?

10 years ago

I changed my answer to match yours and yours were all wrong, mine were right, thanks for posting false information!!! I only wanted to double check my work!!! Wish I would have seen these comments before!

10 years ago

But I can't understand that solution , I mean where is it from :(( m*3.3E5= )) ?

10 years ago

We have this main law : dPE + dkE + dU = 0 but what about the potential energy (dPE) ?

10 years ago