题目

若20g密度为ρg•cm﹣3的硝酸钙溶液里含0.5gCa2+，则NO3﹣的物质的量浓度是（ ）A.2.5ρmol•L﹣1 B.mol•L﹣1C.1.25ρmol•L﹣1 D.mol•L﹣1 答案：【答案】C【解析】0.5g Ca2+的物质的量为=0.0125mol，溶液中n（NO3﹣）=2n（ Ca2+）=0.0125mol×2=0.025mol，溶液体积为=L，NO3-的物质的量浓度为=1.25ρmol/L，答案选C。 Recently quite a lot of exports _______ that another law on wildlife protection ________ as soon as possible .A．demanded , must be passedB．have demanded, be passed C．were demanding , was passedD．demanded, being passed