A:1/2 N2H4(g)+1/2O2(g)==='1/2' N2(g)+H2O(g)ΔH=+267 kJ·mol-1
B:N2H4(g)+O2(g)===N2(g)+2H2O(l)ΔH=-133.5 kJ·mol-1
C:N2H4(g)+O2(g)===N2(g)+2H2O(g)ΔH=+534 kJ·mol-1
D:N2H4(g)+O2(g)===N2(g)+2H2O(g)ΔH=-534 kJ·mol-1
对下列与压强有关的事例.解释不正确的是( )
读“我国外流区和内流区示意图”,回答下列问题。
47+29=____ 6+57=____ 40-18=____ 65-56=____
39+57-21=____ 52-(60-24)=____ 71-15-26=____ 91-58+17=____
若a:b:c=2:3:7,且a-b+3=c-2b,则c=( )