题目

 Linda is fifteen ____. She is in Class 1, Grade 9. A. year                    B. years                        C. years old           D. year old 答案：C9．表中某些共价键的键能，由此判断下列说法不正确的是（　　）共价键H-HF-FH-FH-ClH-IE（kJ•mol-1）436157568432298A．432kJ•mol-1＞E（H-Br）＞298kJ•mol-1B．H2（g）+F2（g）=2HF（g）△H=25kJ•mol-1C．表中最稳定的共价键是H-FD．H2（g）→2H（g）△H=+436kJ•mol-1