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(14-1) Determine whether an acid is strong or weak is extremely important in chemistry




(14-1) Determine whether an acid is strong or weak is extremely important in chemistry. Acids and bases are extremely useful reagents in making other products.;H2SO4 versus HCl;1) The first step in determining whether one acid is stronger than the next is to write out the reactions. Let's compare H2SO4 versus HCl. Both are considered strong acids. That means both will ionize almost completely in water.;HCl ---> H+ + Cl-;One mole of HCl will yield almost 1 mole of H+;but;H2SO4 ------> 2H+ + SO42-;One mole of H2SO4 will yield almost about 1.7 moles of H+;then pH[HCl] > pH[H2SO4];note;HSO4- -------> H+ + SO42-, goes to about 70% completion.;2) The second step is to compare the pKa values. This can be found on the Internet.;3) But, the pKa value of HCl suggests that it is a stronger acid than H2SO4.;4) Then, you consider other factors. H2SO4 can contribute 2 H+. Both pKa values for H2SO4 and HSO4- are pretty good (just not as good as HCl). But together, they contribute more H+. Therefore, H2SO4 will have a lower pH than HCl, making H2SO4 a stronger acid.;(16-1) Please define oxidation and reduction in terms of electron transferred and in terms of oxidation numbers.;Choosing one of the reactions below, please identify the substance being oxidized and the substance being reduced. (Try to pick one that hasn't been done by a classmate.);Write out the half-reactions (oxidation part and the reduction) for that reaction. This will help you in your text assignment for this week.;1. Zn(s) + O2(g) --> ZnO2(s);2. CH4(g) + 2O2(g) --> CO2(g) + 2H2O(g);3. Sr(s) + F2(g) --> SrF2(s);4. 2Sr(s) + O2(g) --> 2SrO(s);5. Ca(s) + Cl2(g) --> CaCl2(s);6. Ni2(aq) + Mg(s) --> Mg2+(aq) + Ni(s);7. Mg(s) + Br2(g) --> MgBr2(s);8. 2Cr3+(aq) + 3Mn(s) --> 2Cr(s) + 3Mn2+(aq);9. 2H+(aq) + Ni(s) --> H2(g) + Ni2+(aq);10. 2H2(g) + O2(g) --> 2H2O(l);11. 4Al(s) + 3O2(g) --> 2Al2O3(s);12. 2Al(s) + 3Cl2(g) --> 2AlCl3(s)


Paper#16508 | Written in 18-Jul-2015

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