Công thức giải nhanh tăng giảm khối lượng

By Trang Ánh Nam -


Cho 5,1 gam hỗn hợp X gồm Al và Mg tác dụng vừa đủ với dung dịch HCl thấy khối lượn tăng lên 4,6 gam. Tính khối lượng từng kim loại trong hỗn hợp đầu.
Phương trình phản ứng:
KL + HCl -->KLClx +H2.
Áp dụng định luật bảo toàn khối lượng ta có:
mkl +mddHCl =mddmuối +mH2.=
=>mddmuối -mddHCl =mkl -mH2
ở đây ta lưu ý :
ü trong lọ của mình ban đầu chứa ddHCl sau đó trong lọ chứa dd muối nên:mtăng= mddmuối -mddHCl
ü kl mình cho vào lọ chứa dung dịch HCl nên ta có thể xem là mvào
ü H2 bay ra khỏi lọ nên ta xem là mra
Tóm lại: mtăng= mddmuối -mddHCl=mkl -mH2
Hay: mtăng=mvào-mra.
Áp dụng: 4,6=5,1-mH2 =>mH2=0,5

Tới đây đặt x,y lập hệ là xong.

Tương tự ta cũng có công thức khối lượng giảm:
Mgiảm=mra-mvào.

Nếu muốn xem những công thức giải nhanh khác thì vào đây: Xem

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