推荐回答(5个)
1.元素守恒,质量守恒.化学方程式左边有2个X ,6个Y ,而化学方程式右边有2个Z. 所以Z等于XY3
2. 化学方程式左边有4个C ,12个H.所以右边也应该有4个H,12个H .又因为X前的系数是2,所以X是 C2H6
3.木炭在氧气中燃烧生成二氧化碳的化学方程式: C + O2 =CO2 (条件点燃)
C的相对分子质量是12,氧的是16,所以12gC和32gO反应才生成44gCO2.根据以上比例列等式.A中实际反应的氧气没有8g,所以错.以次类推,C为正确答案!
4.开始A有20g ,反应后A有10g,则A反应了10g. C,D为生成物,则开始时C,D的量为0.现反应后有C 8g,则C生成了 8g.因为 B物质反应完,则B反应了5g. 再根据质量守恒,A+B=C+D. 所以D生成了 (10+5)-8=7g. 所以A:B:C:D =10:5:8:7
5.还是根据质量和物质守恒,反应前后反应物和生成物的总质量和元素种类不变!所以呢...先看化学方程式右边有6个K ,左边有1个,因为X前的系数是5,所以X中的K有1个,又因为化学方程式右边有6个I 而左边只有一个,所以X中的有1个..其他的元素已守恒,所以选B答案!
1.C 根据元素守恒,Z=0.5*(2*X+3*2*Y)=XY3
2.D 根据元素守恒,反应前和反应后的元素不变,解法和第一题一样.
3.C 质量守恒定律,根据C在O2中充分燃烧的方程式:C+O2=CO2得知,6gC和16gO2恰好完全反应,生成22gCO2
4.B 根据质量守恒定律,可以得出,A=10g C=8g B=5g D=A+B-C=10+5-8=7g 比值为10:5:8:7
5.B 根据元素守恒,得知X中必含I,因为右边有6个I,左边的KIO3只有一个.加之X中含有一个I,刚好5X中有五个I.所以答案为B
自己做了一下,但愿做对了.
哈哈,最近得了市级一等奖,哈哈.
第一题:原子守恒,两个z里应有2个x,6个Y,除以二,z就是C.XY3
第二题:选D,原子守恒
第三题:C+O2=CO2 M(C)=12 M(O)=16 M(CO2)=44,选C
第四题:选B B的5g完全反应,A有10g参加反应,总15g。反应生成C 8g,D为15-8=7g
第五题:B
第一题..质量守恒...所以XY3
第二题..同样质量守恒...D
第三题...根据方程式..判断过量..按不足的算..C
第四题...相同原理 ..B
第五题B 可以主要注意一下I的个数!
1.根据原子守恒定律,根据反应方程式可知X:Y=1:3,所以Z=XY3
2.根据原子守恒定律,反应式右边总共包含了4个C,12个H,14个O,
所以2X应该包含4个C与12个H,X自然就是C2H6
3.C+O2=CO2,C与O2要完全反应生成CO2其质量比例应为12:32=3:8
符合这一比例的是C选项
4.质量守恒定律,即反应前后总的质量不变。
20+5=10+8+D,可算出D=7,从反应后的物质中有A 10g ,C 8g。发现B物质已反应完, 这句话可以知道,A+B=C+D中A反应了20-10=10,B反应了5,生成C为8,生成D=7,所以10:5:8:7是正解
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