x*****8 发帖数: 10683 | 1 上次一个美女学生AP Chemistry预测盐溶液的pH。
其中一道题是: Na2SO4
我告诉她:It's exactly 7 since NaOH is a strong base, while H2SO4 is a
strong acid.
当时她将信将疑。
今天她毫不客气地说:I think you were wrong last time. My friends and my
teacher all told me the pH should be higher than 7 since the conjugate acid
of SO4 2- is HSO4 -, which is a weak acid, while the conjugate base of Na +
is NaOH, which is a strong base.
我厌恶地说:If you don't agree with what I said, then please find a
different teacher!
我心里很清楚我是正确的,她的同学和老师都错了!硫酸钠是强酸硫酸和强碱氢氧化钠
形成的盐,pH当然是中性的。你不能因为硫酸的第一步离解算强酸而硫酸的第二步离解
算弱酸就得出硫酸钠水溶液略偏碱性的错误结论!
不听我话的,再漂亮我也不教! | h**c 发帖数: 1979 | | x********e 发帖数: 35261 | 3 说明你根本就没把别人教懂啊
acid
+
【在 x*****8 的大作中提到】 : 上次一个美女学生AP Chemistry预测盐溶液的pH。 : 其中一道题是: Na2SO4 : 我告诉她:It's exactly 7 since NaOH is a strong base, while H2SO4 is a : strong acid. : 当时她将信将疑。 : 今天她毫不客气地说:I think you were wrong last time. My friends and my : teacher all told me the pH should be higher than 7 since the conjugate acid : of SO4 2- is HSO4 -, which is a weak acid, while the conjugate base of Na + : is NaOH, which is a strong base. : 我厌恶地说:If you don't agree with what I said, then please find a
| x*****8 发帖数: 10683 | 4 这位美女只信她高中AP化学老师教的。
我们在中国高中和大学化学学的原理很简单:
强酸强碱形成的盐不水解,pH中性。
强酸弱碱形成的盐水解,pH偏酸性。
强碱弱酸形成的盐水解,pH偏碱性。
连美国的AP Chemistry大纲上也是这么写的。
这位美女的高中AP化学老师竟然让她先找出这个盐的conjugate base和conjugate acid
,再比较强弱。这个方法既麻烦又不靠谱。
【在 x********e 的大作中提到】 : 说明你根本就没把别人教懂啊 : : acid : +
| d****o 发帖数: 32610 | 5 我咋记得高中把硫酸氢根算完全电离
acid
+
【在 x*****8 的大作中提到】 : 上次一个美女学生AP Chemistry预测盐溶液的pH。 : 其中一道题是: Na2SO4 : 我告诉她:It's exactly 7 since NaOH is a strong base, while H2SO4 is a : strong acid. : 当时她将信将疑。 : 今天她毫不客气地说:I think you were wrong last time. My friends and my : teacher all told me the pH should be higher than 7 since the conjugate acid : of SO4 2- is HSO4 -, which is a weak acid, while the conjugate base of Na + : is NaOH, which is a strong base. : 我厌恶地说:If you don't agree with what I said, then please find a
| x*****8 发帖数: 10683 | 6 你查查HSO4- 的Ka值,不算完全电离。
这个同学的老师错就错在:算盐水解的时候,不应该考虑硫酸氢根的电离不完全,应该
假设它完全电离。
【在 d****o 的大作中提到】 : 我咋记得高中把硫酸氢根算完全电离 : : acid : +
| t*d 发帖数: 1760 | 7 妈蛋太假了,那个电脑的苹果标都歪了
【在 h**c 的大作中提到】
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