14+25+56 ____ 155
78 ____ 13+12−524
已知a+b=3,ab=2,则代数式(a﹣2)(b﹣2)的值是____
已知热化学方程式:① C2H2(g) +52O2(g) == 2CO2(g)+H2O(l) ΔH1=-1301.0 kJ•mol-1② C(s)+ O2(g) == CO2(g) △H2=-393.5 kJ•mol-1③ H2(g)+ 12O2(g) == H2O(1) △H3 = -285.8 kJ·mol-1则反应④ 2C(s)+ H2(g) == C2H2(g)的△H为( )
The Internet is very useful for us. We can _______ find information we need.