题目

The teacher told us that light  _____  much faster than sound.      A .travels   B . travelled  C .would travel  D . had travelled 答案：A根据表数据，下列判断正确的是（　　）电离常数（25℃）HF：Ka1=3.6×10-4H3PO4：Ka1=7.5×10-3Ka2=6.2×10-8Ka3=2.2×10-13 A、在等浓度的NaF、NaH2PO4混合溶液中，c（Na+）+c（H+）=c（F-）+c（H2PO4-）+c（OH-）B、少量H3PO4和NaF反应的离子方程式为：H3PO4+F-→H2PO4-+HFC、同温同浓度时，溶液的pH：NaF＞NaH2PO4＞Na2HPO4D、结合H+的能力：PO43-＞F-＞HPO42-