с:8*25=1000               510-9*у=438                        а*12:18=468 заранее спасибо)

Сложить уравнение реакций,при помощи каких возможно осуществить преобразование:

MgCO3 => CO2 => CaCO3 =>Ca(HCO3)2 => CaCO3 =>CO2 

№1.
 Вычислите массу минерала халькозина , содержащего 80% сульфида меди(1) , необходимого для получения 196 т "башенной серной кислоты" (75%-го раствора серной кислоты),считая,что выход продукта от теоретич.возможного составит 80%.

№2.

какая масса серного ангидрида и какая масса 10%-го раствора потребуется для приготовления 20%-го раствора серной кислоты массой 200 г?

№3.

Навеску смеси сульфата натрия ,нитрата натрия и карбоната натрия массой 56 г растворили в воде и обработали избыточным количеством раствора нитрата бария . В результате реакции образовался осадок массой 69.9 г. Если точно такое же количство смеси обработать избытком соляной кислоты , то выделяется газ объемом 2,24 л .Вычислите массу компонентов в порции исходной смеси.

Выручайте ребят!!!))))))

You are going to read an article about a woman pilot. Eight sentences have been removed from the article. Choose from the sentences A-1 the one which fits each gap (15-21). There is one extra sentence which you do not need to use.

15__ It ended only three days behind schedule when she landed her Piper Dakota at Birmingham in central England in May, five months later. 16__ This included storms and a cyclone in Fiji, a country in the South Pacific Ocean. Nor was the journey without incident for Polly, who only learned to fly at the age of forty-nine. One of the trip's most frightening moments came, on the same route where Amelia Earhart, the American pilot, went missing when she was attempting to fly around the world in 1937. 17__ In fact, she allowed herself to be photographed as she stood beside a Banyan tree, which Amelia Earhart had planted in 1935, before setting off for the 16-hour section of her flight from Hawaii to California. According to Polly all went well for the first part of her journey. 18__Then suddenly it started to get very bumpy. Checking the outside air temperature Polly discovered it was zero degrees. To her horror she found streams of ice- cold rain running back along the wings and starting to freeze. 19__ Though Polly immediately dropped her height to prevent the weight of ice pulling her plane into the ocean, there was more drama when the cabin suddenly went quiet. 20__ As a result the main tank had run dry an hour early, but fortunately the emergency tank went into action and she was able to land safely. The lonely hours spent flying were a great contrast to the warm welcome she received wherever she landed. 21__ The publicity she attracted also raised money for a charity which provides flying scholarships for disabled people.

A. Polly`s 46`000km record-breaking journey began in January

B. This is the most dangerous kind of ice as it is difficult to see it forming.

C. Polly, however, was determined not to let what had happened in the past cause her anxiety.

D. Strong winds meant that she used more fuel than expected.

E. Up there in sky you are completely free. F. The delay was the result of uncooperative weather.

G. There was tremendous media interest and on one occasion she gave up to seven interviews in a single day.

H. The moon and the stars appeared and she even had time to do some sewing.

Найдите площадь правильного n-угольника, если n=4, r=6см, где r- радиус окружности, вписанной в данный многоуольник. С рисунком пожалуйста, помогите!