下列物质中,属于纯净物的是( )
A.漂白粉
B.汽油
C.硫酸铜
D.矿泉水
答案:C
漂白粉是氯化钙与次氯酸钙的混合物;汽油是各种烃的混合物;矿泉水中含多种可溶性物质,属于混合物。
填方路基应事先找平,当地面坡度陡于()时,需修成台阶形式。
A.1:10
B.1:8
C.1:6
D.1:5
待测粉末与硫酸共同振摇,过滤,以硫酸冲洗滤器。()
A.Shake the powder being examined with chloroform, filter and reserve the extracted powder.
B.Shake the powder being examined with chloroform, filter and evaporate almost to dryness on a water bath.
C.Heat the powder being examined with a mixture of water and hydrochloric acid in a water bath.
D.Heat the powder being examined to boiling with a mixture of ethanol and water.
E.Shake the powder being examined with sulphuric acid, filter and wash the filter with sulphuric acid.