객관식
Approximately how many times heavier is a helium (He) atom compared to a hydrogen (H) atom?
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2. Atoms & Elements
Atomic Mass
객관식
In the nuclear fission reaction n + 235U → 92Kr + 141Ba + 3n, which of the following is the atomic mass (x) of krypton (Kr) produced?
A
3
B
141
C
92
D
235
검증된 단계별 안내1
Identify the given nuclear fission reaction: \(n + {}^{235}U \rightarrow {}^{x}Kr + {}^{141}Ba + 3n\).
Recall that in a nuclear reaction, both the total atomic number (number of protons) and the total mass number (number of protons + neutrons) are conserved.
Use conservation of mass number: The sum of the mass numbers on the left side must equal the sum on the right side. On the left, the mass numbers are \(1\) (for the neutron) and \(235\) (for uranium), totaling \(236\).
On the right side, the mass numbers are \(x\) (for krypton), \(141\) (for barium), and \(3 \times 1 = 3\) (for the three neutrons). Set up the equation: \(236 = x + 141 + 3\).
Solve for \(x\) by rearranging the equation: \(x = 236 - 141 - 3\). This value of \(x\) is the atomic mass number of krypton produced.
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