Boron là nguyên tố có nhiều tác dụng đối với cơ thể người như: làm lành vết thương, điều hoà nội tiết sinh dục, chống viêm khớp,... Do ngọn lửa cháy có màu lục đặc biệt nên boron vô định hình được dùng làm pháo hoa. Boron có hai đồng vị là 10B và 11B, nguyên tử khối trung bình là 10,81. Tính phần trăm số nguyên tử mỗi đồng vị của boron.
1. % 10B = %.
Hãy suy nghĩ và trả lời câu hỏi trước khi xem đáp án
Vậy phần trăm số nguyên tử của đồng vị $^{11}B$ là 100 - x.
Ta có phương trình: $\frac{10x + 11(100-x)}{100} = 10.81$
$\Leftrightarrow 10x + 1100 - 11x = 1081$
$\Leftrightarrow -x = -19$
$\Leftrightarrow x = 19$
Vậy % $^{10}B$ = 19% và % $^{11}B$ = 81%.
Câu hỏi liên quan
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Recognizing these limitations, (22) ________. Many developers are focused on refining AI interactions to be more accurate and ethically sounD. As technology progresses, the integration of AI tools into human workflows is expected to become increasingly seamless. Virtual assistants may soon become even more integral to daily life, assisting with a broader range of personal and professional needs.
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Read the following passage about Healthy Benefits of Yoga and mark the letter A, B, C or D on your answer sheet to indicate the best answer to each of the following questions from 23 to 30.
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Improved flexibility is one of the first and most obvious benefits of yoga. During your first class, you probably won’t be able to touch your toes. But if you stick with it, you’ll notice a gradual loosening, and eventually, seemingly impossible poses will become possible. Each of the yoga poses is built to reinforce the muscles around the spine, the very center of your body, which is the core from which everything else operates.
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Yoga gets your blood flowing. More specifically, the relaxation exercises you learn in yoga can help your circulation, especially in your hands and feet. Yoga also gets more oxygen to your cells, which function better as a result. Twisting poses are thought to wring out venous blood from internal organs and allow oxygenated blood to flow in once the twist is released. Many studies found that a consistent yoga practice improved depression and led to greater levels of happiness and better immune function.
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- Remember to drink enough water, (9) _______ it is crucial for your health and helps keep you energized.
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Choose the word or phrase (A, B, C, or D) that best fits each space in the following passage.
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There are all sorts of things that can (18)____about this special relationship. It may be the result of enjoying the same activities and sharing experiences. Most of us have met someone that we have immediately felt relaxed with as if we had known them for ages. However, it really takes you years to get to know someone well (19)___to consider your best friend.
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Yếu tố chính nào của bài thơ Tiếng thu được đề cập đến trong văn bản này?
Hình chiếu phối cảnh được xây dựng bằng phép chiếu:
Cho phản ứng sau:
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Biến thiên enthalpy chuẩn của phản ứng tính theo nhiệt tạo thành là
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Mark the letter A, B, C, or D on your answer sheet to indicate the correct option that best fits each of the numbered blanks from 18 to 23.
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Finally, music connects us with other cultures. Through music, we can learn about the traditions, feelings, and (21) _______. It’s like traveling to new places without leaving (22) _______. We can hear different instruments, rhythms, and voices that tell us about the rich diversity of our world.
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Tính thể tích khối chóp \(S. A B C D\).