现有24 mL浓度为0.05 mol·L-1的Na2SO3溶液恰好与20 mL浓度为0.02 mol·L-1的K2Cr2O7溶液完全反应。已知Na2SO3可被K2Cr2O7氧化为Na2SO4,则元素Cr在还原产物中的化合价为( ) A.+2 B.+3 C.+4 D.+5 答案:B
16.He looked around and caught a man _______ his hand into the
passenger's pocket.
A.put
B.to be putting
C.to put
D.putting