Fluorine-18 is a radioactive isotope of the element fluorine. According to Wikipedia, its half-life is 109.771 minutes, which means the amount present is halved every 109.771 minutes.
You can use the formula for half-life, such that
. You begin with 135 mg fluorine-18. We don't even need to plug in to the formula to see that after 110 min, the amount has halved to equal
67.5 mg.
Answer:
the plates move which causes an earthquake.
Explanation:
i learned about this.
The coefficient for aluminium is 4.
Explanation:
We have the following chemical reaction:
Al + O₂ → Al₂O₃
In order to balance the chemical equation the number of the atoms entering the reaction should be equal to the number of atoms leaving the reaction.
2 Al + 3/2 O₂ → Al₂O₃
However we need integer numbers so we multiply everything with 2.
4 Al + 3 O₂ → 2 Al₂O₃
The coefficient for aluminium is 4.
Learn more:
about balancing chemical equations
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The answer to the question is a.
Answer:
Two significant figures
Step-by-step explanation:
In <em>multiplication </em>problems, your answer can have no more significant figures than the number with the <em>fewest significant figures</em>.
2.05 cm × 32 cm = 65.600 000 00 cm² (by my calculator)
There are three significant figures in 2.05, but only two in 32.
You must round to <em>two</em> significant figures and report the answer as 66 cm².
65.600 000 00 cm² ⟶ 66 cm²