Cho 5,4 gam kim loại R (có hóa trị III, không đổi) tác dụng vừa đủ với 6,72 lít khí Clo (đktc) ở to cao. Sản phẩm thu được hòa tan vào nước thu được 150 g dd A và cho PƯ với dd 200g NaOH 14% sau PƯ thu được kết tủa B, dung dịch C. Xác định kim loại R. Tính mB , C% dd C

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e

answeridentity;

nuclear fission produces elements that are heavier than helium.

the elements that are used in nuclear fission and their products are much heavier than helium.