A、c( Na+)=
=1mol/L,该溶液的物质的量浓度为0.5mol 0.5L
×1mol/L=0.5mol/L,故A错误;1 2
B、由0.5mol Na+可知Na2SO4的物质的量为0.25mol,硫酸钠的质量为0.25mol×142g/mol=35.5g,故B错误;
C、0.5L中含有35.5gNa2SO4,则配制0.1L需要25.5g×
=7.1gNa2SO4,故C正确;0.1 0.5
D、量取100mL该溶液倒入烧杯中,烧杯中Na+的物质的量为0.5mol×
=0.1mol,故D错误;0.1 0.5
故选C.