中学化学计算基本方法.ppt
中学化学计算基本方法l物质的量关系l【例1】加热分解5 g固体化合物得到A气体0.7L（标准状况）和4 g残渣，A的相对分子质量为。l【解】相对分子质量数值上等于其摩尔质量ln(A)=0.7L/22.4molL-1lM(A)=1/n(A)=32g/moll【例2】取1.5mol/L的硫酸11.5mL，投入0.4 g镁条，再滴入1mol/L NaOH溶液将溶液中的Mg2+全部沉淀下来，NaOH溶液的用量至少为mL。l本题涉及到的反应一定有：lMg+H2SO4=MgSO4+H2lMgSO4+2NaOH=Mg(OH)2+Na2SO4l可能有:lH2SO4 2NaOHNa2SO42H2Oln(H2SO4)=l1.5mol/L 11.5mL10-3L/mL2l=0.0345moll守恒法的应用l【例3】Na2S2O3与Na2S的混合物3.14 g溶于足量盐酸中，计算最多可产生单质硫多少克？l【解】所谓最多就是3.14 g混合物中的S全部沉淀，等价于S2O32-与S2-在酸性条件下直接反应且二者均不过量lS2O32-+2S2-+4H+=3S+3H2Ol推得S2O32-和S2-的物质的量之比为1：2.容易计算出最多可生成S 1.28 g.l【例4】在10mL的试管中充有NO2和O2的混合气体。将试管口插入水中，结果试管内气体剩余1mL。计算混合气体中NO2的体积。l本题涉及到的化学反应方程式为l3NO2+H2O=2HNO3+NOl2NO+O2=2NO2l直接推得物质的量关系：l4NO2+O2+2H2O=4HNO3l（1）若剩余气体为1mLO2l其余的9mL NO2、O2气体按4：1的比例分配lV（NO2）=9mL4/5=7.2mLl（2）若剩余气体为1mLNOl根据3NO2+H2O=2HNO3+NO可知，原NO2相对于O2过量3mLl(a-3):(10-a)=4:1la=8.6mLl【例5】用含铁28%的黄铁矿（主要成分为FeS2，杂质不含S）800t，若在制取硫酸的三个流程中共损失硫元素7%，计算能制得98%的浓硫酸多少吨。l物质的量关系有以下几种：lFeS2 2H2SO4 lS H2SO4 lFe FeS2 2H2SO4 l列式为：l5656：298=80028%298=80028%（1-7%1-7%）：）：x x98%98%l【例6】某硫酸溶液40mL，向其中加入1.60 gFe2O3,全部溶解，再向其中加入5.00g铁粉，溶液变成浅绿色。反应停止后还剩余3.32 g铁粉，求此硫酸的物质的量浓度。l本题涉及三个反应式：lFe2O3+3H2SO4=Fe2(SO4)3+3H2OlFe+Fe2(SO4)3=3FeSO4lFe+H2SO4=FeSO4+H2lc(H2SO4)=(1.6/1602+（5.00-3.32)/56）/0.04=1.25 mol/Ll【例7】将0.8molCO2通入到1L 1mol/L的NaOH溶液中，充分反应后，溶液中HCO3-和CO32-的物质的量浓度之比为多少？l【解】按元素物质的量守恒配平下式：l0.8CO2 NaOHl xNaHCO3+yNa2CO3+(1-x)/2H2Ol则有：x+y=0.8 x+2y=1lx=0.6 y=0.2 l【例8】将两个铂电极插入500mLCuSO4溶液中进行电解，通电一段时间后，某一电极增重0.064 g（设电解时该电极无氢气放出，且不考虑水解和溶液体积变化。此时溶液中氢离子浓度为多少？l电极反应：l阴极：2Cu2+4e-=2Cul阳极：4OH-4e-=2H2O+O2ln(H+)=0.064g/64g/mol=0.002mollc(H+)=0.002mol/0.5L=0.004mol/Ll【例9】在三个密闭容器内分别装有：（A）Na2O2和NaHCO3（B）Na2O2和NH4HCO3（C）Na2O2和Ca(HCO3)2，其中每种物质均为1mol。将它们加热至300，经充分反应后排出气体。写出各容器内残留的固体物质名称及其物质的量。l反应式：2NaHCO3=Na2CO3+H2O+CO2l2Na2O2+2CO2=2Na2CO3+O2l2 H2O+2Na2O2=4NaOH+O2lNa2CO3和NaOH各1moll【例10】将铁和氧化铁的混合物共54.4 g，投入到400mL某浓度的稀硫酸中，固体恰好完全溶解。充分反应后收集到4.48L标准状况下的氢气4.48L，向剩余溶液中滴入KSCN溶液，不显红色。l求：（1）原混合物中铁和氧化铁的质量；l （2）稀硫酸的物质的量浓度。l设铁的物质的量为x mol，氧化铁为y moll56x+160y=54.4 l2x=2y1+4.48/22.42lx=0.4 y=0.2 lm(Fe)=0.456=24.4 glm(Fe2O3)=0.2160=32.0 gl(2)反应后的溶液为FeSO4l设原来硫酸的物质的量为z lz=0.40.22=0.8 mollc(H2SO4)=0.8/(40010-3)=2.0 mol/L差量法的应用l【例11】接触法制硫酸，煅烧FeS2制取的气体中含N278%，O211%，SO27%，CO24%。混合气体进入接触室反应后，气体体积变为原来的96.7%（体积均在相同条件下测得，温度在50以上）。l求（1）SO2的转化率。l （2）反应后O2占总体积的百分数。l若原来为100体积，反应后为96.7体积，则3.3就是所谓的“差量”l2SO2+O2=2SO3 =1lx y 3.3 l2:x=1:y=1:3.3lx=6.6 y=3.3l（1）6.6/7100%94.3l（2）(11-3.3)/96.7100%=7.96%l避开了对SO3产量的计算l【例12】在密闭容器中放入(NH4)2CO3和NaOH两种固体共a g，将容器加热至200，经充分反应后排除其中的气体，冷却，称得剩余的固体质量为b g。问原容器中(NH4)2CO3和NaOH各多少克？l(NH4)2CO3+2NaOH=Na2CO3+2NH3+2H2O =70lx a-x a-bl(1)若反应后NaOH过量，则以(NH4)2CO3为已知列式l96:x=70:(a-b)l(2)若反应后(NH4)2CO3过量，则b g物质均为Na2CO3l（a-x）：40=b/1062l【例13】向含Al3+a mol的氯化铝溶液中滴入含OH-b mol的氢氧化钠溶液，讨论生成氢氧化铝沉淀的物质的量。lAl3+3OH-=Al(OH)3lAl(OH)3+OH-=AlO2-+2H2OlAl3+4OH-=2AlO2-+2H2Ol(1)当a:b1:3时，n=b/3l(2)当a:b1：3时，n=4a-bl注意，n不可能为负值讨论法的应用l【例14】写出H2S燃烧反应的化学方程式。1.0L H2S气体和a L空气混合后点燃，若反应前后气体的温度和压强都相同（20，101.3kPa），讨论当a的取值范围不同时，燃烧后气体的总体积V（用含a的表达式表示。假定空气中氮气和氧气的体积比为4：1,其它成分可忽略不计）。l有关反应式为：l2H2S+O2=2S+2H2O =3l1.0 0.5l2H2S+3O2=SO2+2H2O =3l1.0 1.5l讨论（1）当a20%0.5，即a2.5时，只发生式，设反应后造成的体积差为x L,则应以O2为已知求算。lO2 =3la20%x x=3a/5(L)V总=(1+2a/5)Ll（2）当a20%1.5即a7.5时，只发生式，因O2过量，体积差x应以H2S的量为已知计算l2H2S=3l2 3l1 x=1.5(L)V总=1+a-1.5=(a-0.5)Ll（3）当2.5a7.5时，同时发生和式，且H2S无剩余，但因两反应均有：l2H2S=3 所以计算结果同（2）l综合（2）（3）当a2.5时，lV总=(a-0.5)L(u%rZoWlThQeNbJ8G4D1A-w*t$qYnVjSgPdLaI7F3C0y)v&s#pXmUiRfNcK9H5E2B+x(u$rZoWkThQeMbJ8G4D1z-w*t!qYnVjSgOdLaI6F3C0y)v%s#pXlUiRfNcK8H5E2A+x(u$rZnWkThPeMbJ7G4C1z-w&t!qYmVjRgOdL9I6F3B0y)v%s#oXlUiQfNcK8H5D2A+x*u$rZnWkShPeMaJ7G4C1z)w&t!pYmVjRgOcL9I6E3B0y(v%r#oXlTiQfNbK8G5D2A-x*u$qZnWkShPdMaJ7F4C1z)w&s!pYmUjRgOcL9H6E3B+y(v%r#oWlTiQeNbK8G5D1A-x*t$qZnVkSgPdMaI7F4C0z)v&s!pXmUjRfOcK9H6E2B+y(u%r#oWlThQeNbJ8G5D1A-w*t$qYnVkSgPdLaI7F3C0z)v&s#pXmUiRfOcK9H5E2B+x(u%rZoWkThQeMbJ8G4D1z-w*t!qYnVjSgPdLaI6F3C0y)v&s#pXlUiRfNcK9H5E2A+x(u$rZoWkThPeMbJ7G4D1z-w&t!qYmVjSgOdL9I6F3B0y)v%s#oXlUiQfNcK8H5E2A+x*u$rZnWkThPeMaJ7G4C1z-w&t!pYmVjRgOdL9I6E3B0y(v%s#oXlTiQfNbK8H5D2A-x*u$qZnWkShPdMaJ7F4C1z)w&s!pYmUjRgOcL9I6E3B+y(v%r#oXlTiQeNbK8G5D2A-x*t$qZnVkShPdMaI7F4C0z)w&s!pXmUjRfOcL9H6E2B+y(u%r#oWlThQeNbJ8G5D1A-x*t$qYnVkSgPdMaI7F3C0z)v&s!pXmUiRfOcK9H6E2B+x(u%rZoWlThQeMbJ8G4D1A-w*t!qYnVjSgPdLaI6F3C0y)v&s#pXlUiRfNcK9H5E2B+x(u$rZoWkThQeMbJ7G4D1z-w*t!qYmVjSgOdLaI6F3B0y)v%s#pXlUiQfNcK8H5E2A+x*u$rZnWkThPeMaJ7G4C1z-w&t!qYmVjRgOdL9I6F3B0y(v%s#oXlUiQfNbK8H5D2A+x*u$qZnWkShPeMaJ7F4C1z)s#pXlUiQfNcK8H5E2A+x(u$rZnWkThPeMbJ7G4C1z-w&t!qYmVjRgOdL9I6F3B0y(v%s#oXlUiQfNbK8H5D2A+x*u$qZnWkShPeMaJ7F4C1z)w&t!pYmUjRgOcL9I6E3B0y(v%r#oXlTiQfNbK8G5D2A-x*u$qZnVkShPdMaJ7F4C0z)w&s!pYmUjRfOcL9H6E3B+y(u%r#oWlTiQeNbJ8G5D1A-x*t$qZnVkSgPdMaI7F4C0z)v&s!pXmUjRfOcK9H6E2B+y(u%rZoWlThQeNbJ8G4D1A-w*t$qYnVjSgPdLaI7F3C0y)v&s#pXmUiRfNcK9H5E2B+x(u%rZoWkThQeMbJ8G4D1z-w*t!qYnVjSgOdLaI6F3C0y)v%s#pXlUiRfNcK8H5E2A+x(u$rZnWkThPeMbJ7G4C1z-w&t!qYmVjSgOdL9I6F3B0y)v%s#oXlUiQfNcK8H5D2A+x*u$rZnWkShPeMaJ7G4C1z)w&t!pYmVjRgOcL9I6E3B0y(v%r#oXlTiQfNbK8H5D2A-x*u$qZnWkShPdMaJ7F4C1z)w&s!pYmUjRgOcL9H6E3B+y(v%r#oWlTiQeNbK8G5D1A-x*t$qZnVkSgPdMaI7F4C0z)v&s!pXmUjRfOcL9H6E2B+y(u%r#oWlThQeNbJ8G5D1A-w*t$qYnVkSgPdLaI7F3C0z)v&s#pXmUiRfOcK9H5E2B+x(u%rZoWkThQeMbJ8G4Dw&s!pXmUjRfOcL9H6E2B+y(u%r#oWlThQeNbJ8G5D1A-w*t$qYnVkSgPdLaI7F3C0z)v&s#pXmUiRfOcK9H5E2B+x(u%rZoWlThQeMbJ8G4D1A-w*t!qYnVjSgPdLaI6F3C0y)v&s#pXlUiRfNcK9H5E2A+x(u$rZoWkThPeMbJ7G4D1z-w&t!qYmVjSgOdLaI6F3B0y)v%s#pXlUiQfNcK8H5E2A+x*u$rZnWkThPeMaJ7G4C1z-w&t!pYmVjRgOdL9I6E3B0y(v%s#oXlTiQfNbK8H5D2A+x*u$qZnWkShPeMaJ7F4C1z)w&t!pYmUjRgOcL9I6E3B+y(v%r#oXlTiQeNbK8G5D2A-x*t$qZnVkShPdMaI7F4C0z)w&s!pXmUjRfOcL9H6E3B+y(u%r#oWlTiQeNbJ8G5D1A-x*t$qYnVkSgPdMaI7F3C0z)v&s!pXmUiRfOcK9H6E2B+x(u%rZoWlThQeMbJ8G4D1A-w*t$qYnVjSgPdLaI7F3C0y)v&s#pXmUiRfNcK9H5E2B+x(u$rZoWkThQeMbJ7G4D1z-w*t!qYmVjSgOdLaI6F3B0y)v%s#pXlUiQfNcK8H5E2A+x(u$rZnWkThPeMbJ7G4C1z-w&t!qYmVjRgOdL9I6F3B0y(v%s#oXlUiQfNbK8H5D2A+x*u$qZnWkShPeMaJ7F4C1z)w&t!pYmVjRgOcL9I6E3B0y(v%r#oXlTiQfNbK8G5D2A-x*u$qZnVkShPdMaJ7F4C0z)w&s!pYmUjRfK8H5D2A+x*u$rZnWkShPeMaJ7G4C1z)w&t!pYmVjRgOcL9I6E3B0y(v%r#oXlTiQfNbK8G5D2A-x*u$qZnVkShPdMaJ7F4C0z)w&s!pYmUjRfOcL9H6E3B+y(v%r#oWlTiQeNbK8G5D1A-x*t$qZnVkSgPdMaI7F4C0z)v&s!pXmUjRfOcK9H6E2B+y(u%rZoWlThQeNbJ8G4D1A-w*t$qYnVkSgPdLaI7F3C0z)v&s#pXmUiRfOcK9H5E2B+x(u%rZoWkThQeMbJ8G4D1z-w*t!qYnVjSgOdLaI6F3C0y)v%s#pXlUiRfNcK8H5E2A+x(u$rZoWkThPeMbJ7G4D1z-w&t!qYmVjSgOdL9I6F3B0y)v%s#oXlUiQfNcK8H5D2A+x*u$rZnWkShPeMaJ7G4C1z)wpXlUiRfNcK9H5E2A+x(u$rZoWkThPeMbJ7G4D1z-w&t!qYmVjSgOdL9I6F3B0y)v%s#oXlUiQfNcK8H5D2A+x*u$rZnWkShPeMaJ7G4C1z-w&t!pYmVjRgOdL9I6E3B0y(v%s#oXlTiQfNbK8H5D2A-x*u$qZnWkShPdMaJ7F4C1z)w&s!pYmUjRgOcL9H6E3B+y(v%r#oXlTiQeNbK8G5D2A-x*t$qZnVkShPdMaI7F4C0z)w&s!pXmUjRfOcL9H6E2B+y(u%r#oWlThQeNbJ8G5D1A-w*t$qYnVkSgPdMaI7F3C0z)v&s!pXmUiRfOcK9H6E2B+x(u%rZoWlThQeMbJ8G4D1A-w*t!qYnVjSgPdLaI6F3C0y)v&s#pXlUiRfNcK9H5E2A+x(u$rZoWkThQeMbJ7G4D1z-w*t!qYmVjSgOdLaI6F3B0y)v%s#pXlUiQfNcK8H5E2A+x*u$rZnWkThPeMaJ7G4C1z-w&t!pYmVjRgOdL9I6F3B0y(v%s#oXlUiQfNbK8H5D-w*t!qYmVjSgOdLaI6F3B0y)v%s#pXlUiQfNcK8H5E2A+x*u$rZnWkThPeMaJ7G4C1z-w&t!qYmVjRgOdL9I6F3B0y(v%s#oXlUiQfNbK8H5D2A+x*u$qZnWkShPeMaJ7F4C1z)w&t!pYmUjRgOcL9I6E3B+y(v%r#oXlTiQfNbK8G5D2A-x*u$qZnVkShPdMaJ7F4C0z)w&s!pYmUjRfOcL9H6E3B+y(u%r#oWlTiQeNbJ8G5D1A-x*t$qYnVkSgPdMaI7F4C0z)v&s!pXmUjRfOcK9H6E2B+y(u%rZoWlThQeNbJ8G4D1A-w*t$qYnVjSgPdLaI7F3C0y)v&WlTiQeNbJ8G5D1A-x*t$qZnVkSgPdMaI7F4C0z)v&s!pXmUjRfOcK9H6E2B+y(u%rZoWlThQeNbJ8G4D1A-w*t$qYnVjSgPdLaI7F3C0y)v&s#pXmUiRfOcK9H5E2B+x(u%rZoWkThQeMbJ8G4D1z-w*t!qYnVjSgOdLaI6F3C0y)v%s#pXlUiRfNcK8H5E2A+x(u$rZnWkThPeMbJ7G4C1z-w&t!qYmVjSgOdL9I6F3B0y)v%s#oXlUiQfNcK8H5D2A+x*u$rZnWkShPeMaJ7G4C1z)w&t!pYmVjRgOcL9I6E3B0y(v%r#oXlTiQfNbK8H5D2A-x*u$qZnWkShPdMaJ7F4C1z)w&s!pYmUjRgOcL9H6E3B+y(v%r#oWlTiQeNbK8G5D1A-x*t$qZnVkSgPdMaI7F4C0z)w&s!pXmUjRfOcL9H6E2B+y(u%r#oWlThQeNbJ8G5D1A-w*t$qYnVkSgPdLaI7B+y(v%r#oWlTiQeNbK8G5D1A-x*t$qZnVkShPdMaI7F4C0z)w&s!pXmUjRfOcL9H6E2B+y(u%r#oWlThQeNbJ8G5D1A-w*t$qYnVkSgPdLaI7F3C0z)v&s#pXmUiRfOcK9H6E2B+x(u%rZoWlThQeMbJ8G4D1A-w*t!qYnVjSgPdLaI6F3C0y)v&s#pXlUiRfNcK9H5E2A+x(u$rZoWkThPeMbJ7G4D1z-w&t!qYmVjSgOdLaI6F3B0u%rZoWlThQeMbJ8G4D1A-w*t!qYnVjSgPdLaI6F3C0y)v&s#pXlUiRfNcK9H5E2A+x(u$rZoWkThQeMbJ7G4D1z-w*t!qYmVjSgOdLaI6F3B0y)v%s#pXlUiQfNcK8H5E2A+x*u$rZnWkThPeMaJ7G4C1z-w&t!pYmVjRgOdL9I6E3B0y(v%s#oXlUiQfNbK8H5D2A+x*u$qZnWkShPeMaJ7F4C1z)w&t!pYmUjRgOcL9I6E3B+y(v%r#oXlTiQeNbK8G5D2A-x*t$qZnVkShPdMaJ7F4C0z)w&s!pYmUjRfOcL9H6E3B+y(u%r#oWlTiQeNbJ8G5D1A-x*t$qYnVkSgPdMaI7F3C0z)v&s!pXmUiRfOcK9H6E2B+y(unVkShPdMaJ7F4C0z)w&s!pYmUjRfOcL9H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