Sport is one of the important parts of school life. Twice a week we have physical training lessons. In winter our physical training lessons are held out-of-doors. We go skiing. When it is cold in the street our lessons are held indoors. We have our lessons in our school gymnasium. We play different team games such as basketball or volleyball. Besides, we do some gymnastics. In autumn and in spring, when the weather is warm sometimes we have our physical training lessons at our school stadium. My school has a sports day once a year in late spring. On this day we have no classes. We have different competitions. I like sport and I like physical training lessons.
BaO+Al2O3->Ba(AlO2)2; Надо знать, какая кислота соответствует амфотерному (или кислотному) оксиду. Если не помним, то формулу кислоты легко составить, мысленно прибавив к оксиду воду, просто сложив (Al2O3 + H2O = H2Al2O4, но здесь все индексы четные - поэтому разделим на 2 ) HAlO2 - получили формулу кислоты. теперь легко составить формулу соли, видя, что кислота одноосновная, а барий - двухвалентный. С оксидом цинка еще проще - просто складываем два оксида: BAO + ZnO = BaZnO2 ( кислота, соответствующая оксиду цинка - H2ZnO2)
Twice a week we have physical training lessons. In winter our physical training lessons are held out-of-doors. We go skiing. When it is cold in the street our lessons are held indoors. We have our lessons in our school gymnasium. We play different team games such as basketball or volleyball. Besides, we do some gymnastics. In autumn and in spring, when the weather is warm sometimes we have our physical training lessons at our school stadium. My school has a sports day once a year in late spring. On this day we have no classes. We have different competitions. I like sport and I like physical training lessons.