Một bạn học sinh trộn 14,7 gam kali clorat với 1,3 gam mangan đioxit, được hỗn hợp rắn A rồi cho vào ống nghiệm và nung A để điều chế oxi. Sau khi kết thúc thí nghiệm, trong ống nghiệm còn lại chất rắn B, để nguội rồi cân B thấy khối lượng là 11,392 gam. Tính hiệu suất của phản ứng điều chế oxi.

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