题目

硫代硫酸钠晶体是一种恒温保温瓶的填充物，其化学式为Na2S2Ox．在硫代硫酸钠中硫元素的化合价显+2价．请计算： （1）Na2S2Ox中Na与O元素的质量比为 ； （2）79gNa2S2Ox中含钠元素的质量为 g． 答案：分析：（1）根据在化合物中正负化合价代数和为零列式计算Na2S2Ox中x的值，然后根据化合物中元素的质量比是元素的相对原子质量与原子个数的乘积之比分析； （2）根据化合物中某元素的质量=化合物的质量×该元素的质量分数进行分析． 解答：解：（1）化合物中钠元素常显+1价，氧元素常显﹣2价，听1段对话，回答1-3小题。1. Where are they talking? [     ]A. In the teacher's office.B. In the classroom.C. In the bedroom. 2. Which subject are they talking about? [     ]A. Math. B. English. C. Chinese. 3. What does Jenny think of Mr. White? [     ]A. She thought Mr. White was a very good teacher. B. She thought Mr. White was a very bad teacher. C. Mr. White did many exercises.