【简答题】以硼砂为基准标定HCl溶液,反应为:Na 2 B 4 O 7 +5H 2 O→2NaH 2 BO 3 +2H 3 BO 3 ,NaH 2 BO 3 +HCl→NaCl+H 3 BO 3 。Na 2 B 4 O 7 与HCl反应的物质的量之比为______。
【简答题】1497 年 7 月 8 日 ,葡萄牙国王任命 为探险队队长,再次出航。11 月 22 日 , 船队顺利绕过“ 好望角 ” ,进入印度洋。
【单选题】— Which would you like to drink, coffee, yogurt or orange juice? — . Please give me a cup of tea.
【单选题】单项选择。 I'll take _______, please. [ ]
【简答题】如图,△AOB中,∠AOB=90°,AO=3,BO=6,△AOB绕顶点O逆时针旋转到△A′OB′处,此时线段A′B′与BO的交点E为BO的中点,则线段B′E的长度为____.
【简答题】根据句意及汉语提示完成句子。 1. Try to follow the _____ (节奏), please. 2. Please _____ (去拿来) the bottle for me, Ling Ling. 3. If you have something difficult, please _____ ( 举起) your hand. 4. We _____ (打算) this ne...
【单选题】---Would you please tell me _________? --- In a small village near Niingbo.
A.
where was your mother born
B.
where your mother was born
C.
when was your mother born
D.
when your mother was born
【简答题】以硼砂为基准物标定HCL溶液反应为: Na2B4O7+H2O=2NaH2BO3+2H3BO3 NaH2BO3+HCL=NaCL+H3BO3 Na2B4O7与HCL反应的物质的量之比为:( )
【简答题】如图,在△ABC中,∠A=60°,BO 1 、BO 2 是∠ABC的三平分线,CO 1 、CO 2 是∠ACB的三等分线,则∠BO 1 C=( )°,∠BO 2 C=( )°。