过氧化钙是一种安全无毒的物质,带有数量不等的结晶水,通常还含有部分氧化钙. (1)称取0.542g过氧化钙样品,灼热时发生如下反应: 2(CaO2•xH2O)△2CaO+O2↑+2xH2O,得到的O2在标准状况
过氧化钙是一种安全无毒的物质,带有数量不等的结晶水,通常还含有部分氧化钙.
(1)称取0.542g过氧化钙样品,灼热时发生如下反应:
2(CaO2•xH2O)
2CaO+O2↑+2xH2O,得到的O2在标准状况下体积为67.2ml.该样品中CaO2的物质的量为______.△
(2)另取同一样品0.542g,溶于适量的稀盐酸中,然后加入足量的Na2CO3溶液,将溶液中Ca2+全部转化为CaCO3沉淀,得到干燥的CaCO3 0.70g.
①试计算样品中CaO的质量.
②试计算样品中CaO2•xH2O的x值.
(1)n(O2)=
=0.003mol,0.0672L 22.4L/mol
2(CaO2•xH2O)
2CaO+O2↑+2xH2O
△ .
2mol 1mol
n(CaO2•xH2O) 0.003mol
n(CaO2•xH2O)=0.006mol,
则n(CaO2)=n(CaO2•xH2O)=0.006mol,
故答案为:0.006mol;
(2)n(CaCO3)=
=0.007mol,0.70g 100g/mol
①根据Ca元素守恒,可知:n(CaO)=0.007mol-0.006mol=0.001mol,
m(CaO)=0.001mol×56g/mol=0.056g,
答:样品中CaO的质量为0.056g;
②样品中水的质量为:m(H2O)=0.542g-m(CaO2)-m(CaO)=0.542g-0.006mol×72g/mol-0.056g=0.054g,
n(H2O)=
=0.003mol,0.054g 18g/mol
x=
=n(H2O) n(CaO2)
=0.5,0.003mol 0.006mol
答:样品中CaO2•xH2O的x值为0.5.