why is there a temperature change in acid-base reactions?
97497
There are temperature changes is most reactions becuase there is heat generated, known as the heat of reaction.
289586
The function of a protein depends on its shape.  If you alter the shape of it, you alter its function.  pH is a factor that can alter the shape, because the pKa values of residues on the protein will dictate which residues are or are not protonated, and that will, in turn, affect the manner in which the various amino acids will form internal ionic bonds.\n\nTemperature is another factor.  the stability of intramolecular bonding is dependent on the level of thermal excitation.  If a protein is at a high temperature, the thermal motion of the atoms might upset their abilities to form bonds.  At really high heat, the result will be total denaturation.  At low temperatures, you might even have the opposite problem, with a protein clinging to things in the wrong ways.\n\nFinally, you might alter it by introducing a chemical that reacts with it.  Some proteins need activator molecules to function, others might be inactivated by an inhibitor.  Enzymatic activity occurs in what is called the "active site" of the protein, which is where the substrates bind to the protein and catalysis occurs.  So the activity of the molecule might be altered by changing the arrangement of the moieties in the acive site relative to one another, of there might be a change which permits/blocks access to the active site by the substrate molecules.
903570
Actually HCl is an acid even when it is in the gaseous state. The reaction of HCl gas with NH3 gas gives a cloud of the solid NH4Cl. In this reaction HCl, although it doesn't dissociate, it still donates its H+, so it is an acid according to the Bronsted-Lowry definition.\n\nIf the question is in the context of pH, then you should realize that pH and its 0-14 scale has a meaning only for aqueous solutions, so anyway it is not applicable to gases.\n\nYou should point out this to your teacher, since claiming that HCl gas is not acidic is wrong.
731401
Correct.\nD. when delta G is positive the reaction is non-spontaneous
558851
Two reasons:\n\n1.)  Chemical reactions tend to increase with temperature; the same would be true for chemical weathering.\n\n2.)  Save for deserts, warm areas tend to be rainier, and a warm, wet climate makes for rapid weathering.
873739
The answer is d.) often occurs spontaneously.\n\nThis can be proven from the Gibbs Free Energy equation: \nG = H + TS\n\nwhere G is Gibbs energy, H is enthalpy, T is temperature in Kelvins, and S is the entropy or order of randomness. \nG < 0 is spontaneous\nG > 0 is not spontaneous\n\nIf a reaction releases energy, you can also assume that the reaction is exothermic or releases heat so T (and thus T(S)) in Gibbs equation would be negative, making G < 0, or spontaeous in most cases.
521974
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.
621304
If you are dealing with a reaction involving ammonium carbonate in solution, and are then measuring the temperature rise, you need the heat capacity of water, not ammonium carbonate!\n\nPlease post the whole problem if that is not enough to get you started.
110839
temperature changes de amount of energy in molecules, which has a direct efect on the amount of light transmited through a  solution and, therefore, afects absorbance.  Also, in chemical analysis, the formation of colored compunds is necesary and if the correct temperature is not set, the compound doesn't form correctly. (just some reaction mechanisms from organic chemistry)\nThe AOAC method for testing nitrate content in water is a good example. If you don't give the reaction the correct temperature, the colored compound will never form and the test is invalid.
748799
an acid is a proton donor while a base is a proton acceptor or an electron donor\n Hope i'm right
703155
No surprise at all, the transition does not take place at an pH of exactly 7 but already before. Take a look here for a graph:\n\nhttp://antoine.frostburg.edu/chem/senese/101/acidbase/faq/indicating-strong-or-weak.shtml
361668
A) When temperature is increased the equilibrium shifts right because the left is is warm an unstable so by shifting right it will balance among both sides.\n\nB) Barium nitrate is 100% soluble in water and will therefore act like the products side of the equilibrium (the reactant is solid). The equilibrium shifts left to balance the amount of barium.\n\nC) When Ba(ClO3)2(s) is added the equilibrium shifts right for a similar reason as the first.
588293
When an acid reacts with an alkali (base), neutralisation occurs as the pH of the mixture becomes neutral, pH=7. (Acidic: pH < 7, Basic: pH > 7).\n\nSo an example would be to react sulphuric acid with sodium hydroxide to form sodium sulphate (salt) and water.\n2NaOH + H2SO4 ---> Na2SO4 + 2H20\n\nAn ELEMENT that would neutralise sulphuric acid (i.e. make its pH 7) could be any metal.\n\ne.g. Mg + H2SO4 ---> MgSO4 + H2\n\nBut this is not called a neutralisation reaction.
1142668
Problem \ntake D as Delta(change)\nEstimate the change in enthalpy, DH, for the following reaction:\n\nH2(g) + Cl2(g) --> 2 HCl(g) \n\nSolution \n\nTo work this problem, think of the reaction in terms of simple steps:\n\n\nFirst, the reactant molecules, H2 and Cl2, break down into their atoms\nH2(g) --> 2 H(g)\nCl2(g) --> 2 Cl(g)\n\n\nNext, these atoms combine to form HCl molecules\n2 H(g) + 2 Cl(g) --> 2 HCl(g) \n\nIn the first step, the H-H and Cl-Cl bonds are broken. In both cases, one mole of bonds is broken. When we look up the single bond energies for the H-H and Cl-Cl bonds, we find them to be +436 kJ/mol and + 243 kJ/mol, therefore for the first step of the reaction:\n\nDH1 = +(436 kJ + 243 kJ) = +679 kJ\n\nBond breaking requires energy, so we expect the value for DH to be positive for this step.\n\nIn the second step of the reaction, two moles are H-Cl bonds are formed. Bond breaking liberates energy, so we expect the DH for this portion of the reaction to have a negative value. Using the table, the single bond energy for one mole of H-Cl bonds is found to be 431 kJ:\n\nDH2 = -2(431 kJ) = -862 kJ\n\nBy applying Hess's Law, DH = DH1 + DH2\n\nDH = +679 kJ - 862 kJ\n\nDH = -183 kJ\n\n\nAnswer\n\nDH = -183 kJ
196147
At higher temperatures, reactions proceed faster, so metablic activity increases.  Also, pressure and/or volume may increase.  At high enough temperatures, proteins will start to denature, but this usually doesn't happen with a fever.
701698
The condition for a reaction to proceed spontaneously at constant pressure and temperature is that the change in Gibbs free energy (delta-G) for the reaction is less than zero.\n\nThe Gibbs free energy change is given by:\n\ndelta-G = delta-H - T*delta-S\n\nwhere T is the absolute temperature (i.e., in kelvins).\n\nWe are given delta-H and delta-S for this reaction (the units should probably be in kJ/mole and J/(mol*K) respectively, not J and J/K), and need to find the temperature range (if it exists) for which delta-G is negative.  That is,\n\n0 > delta-G = -5500 J/mol - (-25 J/(mol*K)) * T\n\n5500 K > 25 *T\n\n220 K > T\n\nAnswer (b) is the correct one.
345166
Friction, Heat, Acid.