题目

A hybrid electric vehicle (混合动力车) or HEV is a vehicle driven by the combination of petrol engine and electric motor. Terrence has been driving a HEV for five years. He really doesn’t understand why more people aren’t accepting them. “I probably spend about $ 7 a day on petrol,” the taxi driver told news. com. au. In his previous conventional vehicle Terrence said he was spending up to $ 30 a day on petrol, meaning he saves almost $ 6000 every year.The Toyota spokesman said this was quite a high saving and official tests estimate (估计) an average driver would only save abou实验室有一瓶存放时间过长的氢氧化钠固体，其中一部分已转化成了碳酸钠。现需用该药品配制氢氧化钠溶液。取6克该药品，溶于13.7mL水中（水的密度为1g/cm3），然后慢慢地滴加溶质质量分数为7.4%的澄清石灰水，当用去10克澄清石灰水时，碳酸钠恰好反应完全。计算：（1）6克该药品中碳酸钠的质量；（2）滤出沉淀后所得溶液的溶质质量分数。