A:实验室用Zn和稀硝酸制取H2:Zn+2H+═Zn2++H2↑
B:H2SO4溶液中和Ba(OH)2溶液:H++SO42﹣+Ba2++OH﹣═H2O+BaSO4↓
C:向Ca(HCO3)2溶液中加入过量NaOH溶液:Ca2++2HCO3﹣+2OH﹣═CaCO3↓+CO32﹣+2H2O
D:向苯酚钠溶液中通入少量的CO2:2C4H3O﹣+CO2+H2O═2C6H5OH+CO3﹣2
发电机的发明,开辟了人类电气化的时代,而电动机应用,出现在社会生活的各个方面.如图甲和乙,能说明是电动机工作原理的是____,能说明是发电机工作原理的是____.(以上两空填“甲”或“乙”)
照样子,圈一圈,算一算。
14-9=____(颗)
13-9=____(朵)
圈一圈 ____
He can play the violin _____ he can't play it very well.
8+8=____ 8-8=____ 8÷8=____ 8×8=____