问题
选择题
一种抗生素为粉末状固体，每瓶含0.5g，注射时应配成质量分数为20%的溶液，则使用时每瓶至少需加入蒸馏水（ ）
A．1mL
B．2mL
C．3mL
D．4mL
答案
配制20%的溶液质量=0.5g÷20%=2.5g
则加入蒸馏水的质量=2.5g-0.5g=2g
由于水的密度是1g/ml所以需水的体积是2ml
故选B
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一种抗生素为粉末状固体，每瓶含0.5g，注射时应配成质量分数为20%的溶液，则使用时每瓶至少需加入蒸馏水（ ）
A．1mL
B．2mL
C．3mL
D．4mL
配制20%的溶液质量=0.5g÷20%=2.5g
则加入蒸馏水的质量=2.5g-0.5g=2g
由于水的密度是1g/ml所以需水的体积是2ml
故选B
“Take a walk with any three people and at least one of them will have something to teach you . ” 小题1: it was Confucius（孔夫子） — China’s most famous thinker and teacher. When Confucius was young , he visited many famous teachers and studied music , history , poetry(诗歌) and sports. At the age of 22, he became a teacher himself and started his own school. 小题2: For more than 2000 years, Confucius’ ideas have been around in people’s everyday lives. 小题3: Now they have gone far into east and south Asia. 小题4: Because they help a lot not only in everyday life but also in society. Confucius’ most important ideas are about kindness and good manners. Confucius said young people should take care of the old.小题5: Some of Confucius’ most famous sayings are: “A kind person should care for others”, and “be strict with yourself, but be kind to others”.
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