activation energy for the reverse direction equals 80 kJ/mol. Which side has the greater energy content, the reactants or the product? what is the heat of reaction in the forward direction?
129924
i.e. it is easier to go backwards than forwards, so the product has more energy ( i.e. higher up the energy scale / nearer the top/ easier to get to the transition state ).\n\nHeat of reaction = heats of formation of products - reactants = 85 - 80 = +5kJ mol.... endothermic ( makes sense if products contain more energy than reactants )
327828
This is a calorimetry problem! There is an equation for it:       \nq = mc(change in temperature)\n\nq = the heat required \nm= mass\nc= specific heat \n\nAlso, write out the reaction and products.
505519
Sodium and Potassium are correct.  They are extremely reactive with water, forming Hydroxides and releasing Hydrogen gas, which is usually ignited from the exothermic heat of the reaction.\n\n2 Na + 2 H2O -> 2 NaOH + H2\n\n2 K + 2H2O -> 2 KOH + H2
377289
A reversible reaction can go in both directions.\nAn irreversible reaction cannot.\n\nAn example of a chemical reaction that can go in both directions could be the reactions between rust, hydrogen and water.\nPassing hydrogen gas over rust yields iron and water.\nFe3O4(s) + 4H2(g) --> 3Fe(s) + 4H2O(g)\nBut passing steam over hot iron produces rust and hydrogen.\nFe3O4(s) + 4H2(g) <-- 3Fe(s) + 4H2O(g)\n\nMany oxidation reactions cannot reverse.  For example, burning charcoal on the BBQ will produce ash, CO, CO2 and heat.  However, you cannot use CO2 and ash to make charcoal.  This example is irreversable from a thermodyamic point of view.  Heat is generated from the reaction, yet heat cannot be used to go in the other direction.\n\nReversable thermodynamic processes usually involve a change of state.  You can add heat to change ice to water or water to steam.  Take heat away and you change water to ice.
505326
its actually pretty simple. U multiply by -1 when u flip over an equation...so the reactants become the products and the products the reactants. that way instead of having a negative number u will have a positive number for the kJ. as in this problem. U have to flip #1 so u can cancel a few things with #2. so it becomes..\n1)3 H2O(l) + 2 CO2(g) AH---->CH3CH2OH(l) + 3 O2(g) (multiply by -1 gives u a postive +1367kJ. part two stays the same.\n2) C2H4(g) + 3 O2 ---> 2 H2O(l) + 2 CO2 (g) AH= -1411 kJ\n\nNow the 3 O2 from #1 and #2 cancel since they are on opposite sides. Now the 2 H20 cancel from #2 and you are left with only one in #1 since they are also on opposite sides...which after canceling..leaves u with your original equation.\n\nC2H4(g) + H2O(l) ------> CH3CH2OH(l)\n\nnow since u flipped over #1.....and u have a positive +1367kJ and\n#2 is left the same...its still at negative -1411kJ. u add them together and u get an enthalpy change of -44kJ. sorry its pretty confusing to explain..if anything message me and i willl try to help.
553828
molar mass Fe=55.85\nmoles iron=490/55.85\nmoles iron=8.774\n4 moles are required for the reaction\n8.774/4 provides the number of times the reaction can be completed\nthis equals 2.19\nmultiply this by -1.65103\nand you get -3.62 kJ.  This being negative tells you the reaction is exothermic and that the positive 3.62kJ is the amount given off
73537
1.75mol  /  2mol of C6H6 times specfic heat ( -98.0kJ)\n\n=  .875 * -98.0kJ = -85.75kJ
171488
the reaction is exothermic because the resultant solution or products is warmer than the reactants, assuming that it didn't warm up in the enviroment. In addition all neutralisation reactions are exothermic.\n\nThe solutions were mixed rapidly so that the concentration gradiant increases as quickly as possible preventing the reactants absorbing the heat from the reaction before the reaction is finished.  ie the initial rate of reaction being as high as possible.
365352
Correct.\nD. when delta G is positive the reaction is non-spontaneous
151380
it is based on arrhenius equation\nK=A e ^ (-Ea/RT)\nA- frequency factor\nEa- activation energy (proportional to Delta H)\nR -Gas constant\nT -Temperature\nSince you dont know A- fequncy fator, yu need to do a lengthy calculation\n\nThe modified arrhenium equation will be ( by considering two situations T1, T2 there will be two rates k1, k2 but A-frequency factor is smae for one reaction so it's a constant..)\n\nEa= (R X T1 X T2 X Ln (k1/k2) ) / (T1-T2)\n\nEa= delta H = 17,390 J\nR = 8.314 J/K\nK1 = 1.6 X 10E-4\nK2= ?\nT1 = 298\nT2= 273+97= 370K\n  After substituing all these values, you will get K2= 6.27 E-4\nwhich is in agreement with theory (At high Temperatures, rate should be high..!)\n\nIs this info will help you?\nGood luck!
160015
Try finding the standard reduction potential for Cu and NO first then use those poteintial rxn equ to form the above full reaction afterwhich simply add or substract the poteinital u find to get E for the above reaction. \n\nSince E is proportional to the rate constate, u can use the above concentration as well as partial pressure to calculate the rate constant and hence E. Taking care that rate constant is the concentration/partial pressure of the reactant over the product!
208265
DH reaction = DH products – DH reactants\n\nExample:  2A + B -- C\nDH = DH C – (2 DH A + DH B)\n\nIf DH is negative: exothermic reaction \nIf DH is positive: endothermic reaction
74369
One way to tell is to look up the heats of formation for the reactants and products.  Add all the reactants up and all the products up.  Subtract the reactants from the products.  If the answer is negative, the reaction is exothermic.  \n\nThe other way is to actually carry out the reaction and see if it liberates heat or not.
583378
Total energy at the start is equal to the gravitonal potential energy plus the initial kinetic energy. That equals 320000j + 14400j. At the bottom of the hill, the kinetic energy is 160000j and there is no more potential energy. The amount of energy lost to friction, in the form of heat, is 174400 joules.
241641
Briefly,\na. The equilibrium constant is constant for a particular reaction, hence when more reagent is added, more products are formed. (Equilibrium constant is (product of conc of products/product of concentration of reactants)\n\nb. Each time reacting species collide, they might not have the right orientation or sufficient energy and hence reaction does not always occur.\n\nc. Increasing the temperature by 10 C nearly doubles the rate of a reaction. This is because the fraction of reacting molecules possessing energy higher than the activation energy increases exponentially with rise in temperature. Also the speed of the molecules increases.
74026
The guy who answered before was right but i wanna explain it. An exothermice reaction is one in which heat energy is lost to the surroundings, thus at the end of the reaction, some heat would have been lost. For heat to have been lost, the product has to have lesser heat than the reactant.Take not that heat here is the same as Enthalphy.\nSince the Enthalphy heat value = heat of product-heat of reation = a negative number because heat of product is lesser.\nthus the answer is i nd ii\n\n2. To calculate the heat absorbed or evolved in a system, the formulais Q(quantity of heat) = m*c*T, where m is the mass, c is the specific heat capacity, and T is the change in temperature, thuis this three are neede. Density is not important in this calculation\nso the answwers are i and iii
417814
Quantity of energy lost by the water:\n\nQ = (m)(deltaT)(c)\n    = (50.0g)(2.00 C)(4.18 JK-1g-1)\n    = 418 J\n\nSince the water got colder, the reaction was endothermic, and the enthalpy change for the reaction is +418 J.