已知氧化还原反应：NaNO2+NH4Cl——NaCl+H2O+N2↑，若得到m mol的N2，则电子转移数为__________个，此时氧化产物与还原产物的质量之比为____________。
3MnA 1∶1
从反应方程式可知NaNO2中
被还原成零价，NH4Cl中
被氧化成零价，所以很快可以配平，即：NaNO2+NH4====ClNaCl+N2+2H2O，当得到m mol N2，电子转移数目为3m NA；由上述分析知氧化产物与还原产物均为N2，物质的量之比为1∶1，故其质量之比为1∶1。
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| My First Job I was six when I joined my father and two elder brothers at sunrise in the fields of Eufaula, Okla. __1__ the time I was eight, I was helping dad fix up old furniture. He gave me a cent for every nail I __2__ out of old boards. I got my first __3__ job at JM's Restaurant in town when I was 12. My main responsibilities were __4__tables and washing dishes, but sometimes I helped cook. Every day after school I would __5__ to JM's and work until ten. Even on Saturdays I __6__ from two until eleven. At that age it was difficult going to work and __7__ my friends run off to swim or play. I didn't necessarily like work, but I loved what working allowed me to have. Because of my __8__ I was always the one buying when my friends and I went to the local Tastee Freez. This made me __9__. Word that I was trustworthy and hard-working got around the town. A local clothing store offered me credit __10__ I was only in the seventh grade. I immediately charged a $ 68 sports coat and a $ 22 pair of shoes. I was making only 65 cents an hour, and I already owed the storekeeper $ 90! So I learned early the danger of easy credit. I paid it __11__ as soon as I could. My first job taught me self-control, responsibility and brought me a level of personal satisfaction few of my friends had experienced. As my father, who worked three jobs, once told me, "If you __12__ sacrifice (奉献) and responsibility, there are not many things in life you can't have." How right he was! | |||
| ( ) 1. A. Before ( ) 2. A. pulled ( ) 3. A. usual ( ) 4. A. sweeping ( ) 5. A. head ( ) 6. A. studied ( ) 7. A. helping ( ) 8. A. study ( ) 9. A. proud ( ) 10. A. if ( ) 11. A. far ( ) 12. A. understand | B. Within B. put B. real B. packing B. turn B. worked B. having B. power B. friendly B. while B. in B. require | C. From C. picked C. main C. clearing C. change C. played C. watching C. age C. lucky C. although C. off C. offer | D. By D. pressed D. particular D. emptying D. move D. slept D. letting D. job D. hopeful D. since D. to D. fear |