【查阅资料】① 2NaHCO3 △__ Na2CO3 ＋ CO2 ↑ ＋ H2O ② NaHCO3 ＋ NaOH ＝ Na2CO3 ＋ H2O ③ 2NaHCO3 ＋ Ca(OH)2 ＝ CaCO3 ↓ ＋ Na2CO3 ＋ 2H2O ④ Ca(HCO3)2 ＋ Na2CO3 ＝ CaCO3 ↓ ＋ 2 NaHCO3 ⑤ Na2CO3受热不分解，NaHCO3、Ca(HCO3)2都能溶与水。
58－50=____
7+31=____
43－7=____
6+58=____
65－4=____
32+47=____
When you see an English film or talk with native speakers, observe their facial expressions and g____.
