A：某吸热反应能自发进行，因此该反应是熵增反应
B：NH4F水溶液中含有HF，因此NH4F溶液不能存放于玻璃试剂瓶中
C：可燃冰主要是甲烷与水在低温高压下形成的水合物晶体，因此可存在于海底
D：增大反应物浓度可加快反应速度，因此用浓硫酸与铁反应能增大生成H2的速率
Telephone: 3324545
Address: East Road
Open: Mon. to Fri. 7:30 am—2:30 pm and 5:00 pm—9:00 pm
Sat. 7:30am—2:00pm and 5:00 pm---9:30 pm
Sun. 11:00 am---2:00pm and 5:00 pm –9:30 pm
Telephone: 3351352
Address: Green Road
Open: Mon. to Fri. 9:00 am—5:00 pm(Tuesday free)
Sat. 9:00 am---6:00 pm
Telephone: 3374398
Address: Peace Road
Open: Mon. Wed. and Fri. 9:30 am—5:30 pm
Tues. Thurs. and Sat. 9:30 am ---9:00 pm
Telephone: 3368432
Address: West Road
Coffee shop: Mon. to Fri. 6:00 am
Sat. and Sun. 7:00 am
Mon. to Wed. to 10:00 pm
Thurs. to Sat. to 11:00 pm
Sun. to 9:00 pm.
若x＝3是方程a－x＝7的解，则a的值是（ ）．
计算：﹣3.5+|﹣52|﹣（﹣2）=____ ．
