The half-life of the reaction is 50 minutes
Data;
- Time = 43 minutes
- Type of reaction = first order
- Amount of Completion = 45%
<h3>Reaction Constant</h3>
Let the initial concentration of the reaction be X
The reactant left = (1 - 0.45) X
= 0.55 X
= X
For a first order reaction

<h3>Half Life </h3>
The half-life of a reaction is said to be the time required for the initial amount of the reactant to reach half it's original size.

Substitute the values

The half-life of the reaction is 50 minutes
Learn more on half-life of a first order reaction here;
brainly.com/question/14936355
The answer is 4 (four).
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Answer:
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Explanation:
Atoms are made of 3 types of subatomic particles ; protons, neutrons and electrons
protons and neutrons are located inside the nucleus and electrons are found in energy shells around the nucleus. Protons are positively charged, electrons are negatively charged and neutrons are neutral. elements in their ground state are neutral with equal amounts of protons and electrons.
Atomic number is the number of protons. atomic number is characteristic for the element.
atomic number of Be is 4 therefore Be has 4 protons
answer is B. 4