Câu 24:Khử 6g sắt(III) oxit bằng khí hiđro. Thể tích khí hiđro cần dùng (đktc) là A. 5,04 lít B. 2,52 lít C. 1,26 lít D. 4,2 lít Câu 25: Hòa tan 25 gam muối ăn vào 200 gam nước thu được dung dịch có nồng độ là: A. 7,5% B. 10% C. 2,5% D. 14% Câu 26: Hòa tan 12 gam muối ăn vào 188 gam nước thu được dung dịch có nồng độ là: A. 12% B. 4 % C. 6% D. 10%

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