问题 计算题

(8分)某小组利用下列实验数据,计算金属M的相对原子质量。已知金属M和硫酸反应的化学方程式为: M + H2SO4 ="=" MSO4 + H2↑。现取20 g该金属样品于烧杯中,然后向其中加入稀硫酸,实验数据记录如下:

第5次实验后,烧杯中还有0.5 g剩余固体。

(1)原金属样品中M的质量        

(2)计算该金属的相对原子质量。

答案

(1)19.5g; (2)65

根据实验数据中加入硫酸质量与剩余固体的质量关系,可判断加入500g稀硫酸,样品中金属M完全反应,剩余固体全部为不与硫酸反应的杂质;因此,利用质量守恒定律,可计算金属完全反应时放出氢气的质量;由反应消耗金属的质量及放出氢气的质量,根据反应的化学方程式,可求得该金属的相对原子质量

(1)根据题意,20 g该金属样品中最后还有0.5 g剩余固体不能参加反应,则参加反应的金属质量=20g-0.5g=19.5g,生成氢气的质量500g+20-519.4g=0.6g

(2)解:设该金属的相对原子质量为x

M+H2SO4═MSO4+H2

x              2

19.5g         0.6g

 

x="65"

答:该金属的相对原子质量为65

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