Вопрос школьника по предмету Химия
Определите степени окисления азота в соединениях: NСl3, NO2, NO, Ca3N2, NH3, AlN; HNO3, N2, KNO2.
Ответ учителя по предмету Химия
N⁺³Сl⁻¹₃, N⁺⁴O⁻²₂, N⁺²O⁻², Ca⁺²₃N⁻³₂, N⁺³H⁻¹₃, Al⁺³N⁻³; H⁺¹N⁺⁵O⁻²₃, N⁰₂,
K⁺¹N⁺³O⁻²₂.
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In Russia
children go to school at the age of six or seven. They spend four years at
primary school, five years at secondary school and two years at senior
school.
School normally starts at 8:30 am and finishes at 3 pm through this may
vary slightly from school to school . Young
students have 3-4 lessons a day and older students have up to 7 lessons
a day . This means that the school week can be either 5 or 6 days long . In
large cities where are a lot of students attending the same school there are sometimes separate morning and afternoon
sessions . There are usually around 20-30 students in a class.
There is a wide range of school subjects for students aged 12-17 . These
include Russian,Literature, Maths(including Algebra and Geometry)History,
Social Science, Biology, Geography, Physics, ICT, Chemistry ahd others. English
is the main and most popular foreign language although students can also learn Spanish, German or French. Almost
all classes involve the use of computers and media technology. Some schools may
specialise in certain subjects, Maths and Science, for example. There are also
vocations schools that train students in a specialised profession, such as
music or danse, alongside their usual lessons. The school
year is usually divided into four teams with there breaks. Shool starts on 1st September and finishes on 31st May . The
summer holiday starts on 1st June and lasts for three months but Year 9 and
Year 11 students take their exams in
June. The Russian National Exam is an innovation as a final exam for
school-leavers. Its a national test combining school-leaving exams and entrance
exams to universities
у=4-х^2, у=0;
А Дж,Бруно
Б Р.Декарт
В М.Коперник
Г Г.Галілей