为了检验某含有NaHCO 3 杂质的Na 2 CO 3 样品的纯度,现将w 1 克样品加热,其质量变为w 2 g,则该样品的纯度(质量分数)是(已知:Na 2 CO 3 受热难分解,2NaHCO 3 △ . Na 2 CO 3 +CO 2 ↑+H 2 O)( )
A.
84 w 2 -53 w 2 31 w 1
B.
84( w 1 - w 2 ) 31 w 1
C.
73 w 2 -42 w 1 31 w 1
D.
115 w 2 -84 w 1 31 w 1
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【简答题】One day newly wedded Nancy lost her ring while helping to plant potatoes. Friends were called and the field was searched long but in vain(徒劳). Later, when the potatoes were harvested, Everyone looked ...