Nitrogen trifluoride (NF3) là nguyên liệu được sử dụng trong việc sản xuất pin mặt trời. Phương trình hình thành nitrogen trifluoride được biểu diễn như sau:
N2(g) + 3F2(g) 2NF3(g)
Cho:
Loại liên kết
Năng lượng liên kết (kJ.mol–1)
N≡N
+950
F – F
+150
N – F
+280
Giá trị biến thiên enthalpy chuẩn của phản ứng là bao nhiêu (kJ)?
Nitrogen trifluoride (NF3) là nguyên liệu được sử dụng trong việc sản xuất pin mặt trời. Phương trình hình thành nitrogen trifluoride được biểu diễn như sau:
N2(g) + 3F2(g) 2NF3(g)
Cho:
Loại liên kết |
Năng lượng liên kết (kJ.mol–1) |
N≡N |
+950 |
F – F |
+150 |
N – F |
+280 |
Giá trị biến thiên enthalpy chuẩn của phản ứng là bao nhiêu (kJ)?
Hãy suy nghĩ và trả lời câu hỏi trước khi xem đáp án
Trong đó:
$\sum E_{bonds broken}$ là tổng năng lượng của các liên kết bị phá vỡ ở chất phản ứng.
$\sum E_{bonds formed}$ là tổng năng lượng của các liên kết được hình thành ở sản phẩm.
- Các liên kết bị phá vỡ: 1 mol N≡N và 3 mol F-F
- Các liên kết được hình thành: 6 mol N-F (vì có 2 mol NF3 và mỗi mol NF3 có 3 liên kết N-F)
$\Delta H = [950 + 450] - [1680]$
$\Delta H = 1400 - 1680 = -280 kJ$
Ta có phương trình: N2(g) + 3F2(g) $\rightarrow$ 2NF3(g)
$\Delta H = [E_b(N≡N) + 3*E_b(F-F)] - [6*E_b(N-F)]$
$\Delta H = [950 + 3*150] - [6*280]$
$\Delta H = 1400 - 1680 = -280$ kJ
Vì đề bài không có đáp án nào là -280 kJ, có thể có sai sót trong đề bài hoặc đáp án. Tuy nhiên, tính theo các giá trị năng lượng liên kết đã cho, đáp án gần nhất là -1840 kJ nếu ta xét N2 + 3F2 -> 2NF3. Có lẽ đề bài yêu cầu tính theo một cách khác, hoặc có lỗi trong số liệu.
Do đó, ta cần xem xét lại đề bài hoặc các dữ kiện khác để có thể đưa ra câu trả lời chính xác nhất.
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