Saturday
December 10, 2016

Total # Posts: 111

physic mechanic
All of the following forces are central force, EXCEPT Semua yang berikut adalah daya berpusat KECUALI A)Coulomb force Daya Coulomb B) Frictional force Daya geseran
June 19, 2016

physic mechanic
A particle is pushed horizontally by a constant horizontal force of magnitude F, which starts from the rest at x=0 in the positive ݔ direction. During the movement, it is also acted by the air resistance force that equivalent to bv, where b is the positive coefficient ...
June 19, 2016

physic
A particle is pushed horizontally by a constant horizontal force of magnitude F, which starts from the rest at x=0 in the positive ݔ direction. During the movement, it is also acted by the air resistance force that equivalent to bv, where b is the positive coefficient ...
June 18, 2016

physic
All of the following forces are central force, EXCEPT A)Coulomb force B) Frictional force C)Gravitational force D)Electrostatic force
June 18, 2016

physic
An ant with mass 0.15 g lands on one end of a floating 4.75 g stick. After sitting at rest for a moment, it runs toward the other end with a speed of 3.8 cm/s relative to the river. What is the speed of the stick if it moves in the opposite direction? A) 0.20 cm/s B) 0.16 cm/s...
June 18, 2016

physic mechanic
An ant with mass 0.15 g lands on one end of a floating 4.75 g stick. After sitting at rest for a moment, it runs toward the other end with a speed of 3.8 cm/s relative to the river. What is the speed of the stick if it moves in the opposite direction?
June 18, 2016

Exercise\workout
I have three questions if you please, can I take protein even if with no any workout? can I take amino acid pills in lower dose to meet some deficiencies ? and, can I take protein along with amino acids for bodybuilding ? Thank you so much
April 14, 2016

Physics
A hostess wants to cool her 100g of soup which is currently at 50Celsius, and it's specific heat is 0.8 cal/g celsius, by adding water (specific heat = 1 cal/ g celsius) at a temperature of 5Celsius, how much water should she add, assuming that all the heat from the soup ...
March 2, 2016

Chemistry
N = Sp.gr*1000* percent% / eq.wt Prepare 200 ml of 5 N H2SO4 solution from concentrated H2SO4 , if we know that Sp.gr = 1.84 g/ml , percent = 98% , At.wt for (H= 1 , S=32 , O =16 ) Thank you a lot
March 2, 2016

physics
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
August 26, 2015

physics
We have this main law : dPE + dkE + dU = 0 but what about the potential energy (dPE) ?
August 26, 2015

physics
But I can't understand that solution , I mean where is it from :(( m*3.3E5= )) ?
August 26, 2015

physics
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 10^5 J to melt 1.0 kg ...
August 26, 2015

physics
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 (increasing ) ...
August 26, 2015

science
I want to write a CV , could you help and notice me how to do it ? with respects
June 2, 2015

english language
Are there any tips to help to learn and memorizing the phrasal verbs in english ? With Respects
June 1, 2015

Chemistry
Yes , that's quite right , I actually meant a hexane that has an ethyl group on an its carbon and a double methyl group on another carbon ? with my best respects
April 24, 2015

Chemistry
What is name of this according to the IUPAC: a benzene that has an ethyl group on an its carbon , and a double methyl group on another carbon ? thanks
April 24, 2015

chemistry
I'm confused , can you do the solution please ?
December 18, 2014

chemistry
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
December 18, 2014

math
I can't understand rounding rules of numbers Can you simply explain it ?
November 7, 2014

CHEMISTRY
Does a molecular compound in water have hydration or have ionization ?
September 27, 2014

CHEMISTRY
How can we prepare or change : 1) change unsaturated to saturated soln? 2) change unsaturated to supersaturated? 3) change saturated to unsaturated ? 4) change saturated to supersaturated ? 5) change supersaturated to unsaturated? 6) change supersaturated to saturated ?
September 24, 2014

CHEMISTRY
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 ?
September 24, 2014

CHEMISTRY
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 ) ?
September 24, 2014

CHEMISTRY
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
September 24, 2014

CHEMISTRY
I mean the phase of the gas is going towards being liquid
September 22, 2014

CHEMISTRY
Why dissolving gases in the liquids is exothermic while the phase is down ? explain please
September 22, 2014

CHEMISTRY
but 22.5/58 = 0.3879 , and 0.3879/0.2 = 1.9 but the answer is another (22) .. I can't get it
September 17, 2014

CHEMISTRY
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 .. )
September 17, 2014

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
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

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