Khi hoá hợp 2,1 gam sắt với lưu huỳnh, ngoài tạo ra FeS còn toả ra 1 lượng nhiệt bằng 3,77 kJ. Hiệu suất phản ứng là 100%. Tính nhiệt tạo thành của FeS

7is b8 is d9 is c10 is a11 is d

I'm guessing its b crude oil

The rules are different for multiplication and addition, but the least precise value always restricts the answer. first do the multiplication (as per standard order of operations): 24.6681 × 2.38 ≈ 58.7 since 2.38 has the fewest significant figures, it is considered the lease precise value then do the addition: 58.7 + 332.58 ≈ 391.3 since 58.7 has fewest figures right of decimal it is considered least precise. so final answer: 391.3 with four significant figures.