To answer this question, you need to know the concept of half-life, which is how a radioactive material decreases in mass over time.
The half life of U-235 is 703.8 million years. The first part of this problem is to find the scale factor. To do this, divide the time that has past by the half life, like this:

Now, take this scale factor and multiply it by the current mass, like this:

This number is what you add to the current mass to get the original mass. That is because the scale factor showed us that it was just over one half life. Since after one half life, the mass is cut in half, and this is over one half life, when we add to the original it will be a little over double. This equation illustrates the final addition:

I hope this helped you. Fell free to ask any further questions.
1 mole of reacts with 8 moles of to form 1 mole of and 3 moles of
<h3>What is a tetraphosphorus decoxide?</h3>
Tetraphosphorus decoxide, () is a non-metal oxide that gives acidic property when dissolved in water.
The name phosphorus decoxide can be interpreted as 4 phosphorus (P) atoms (‘Tetra’), bonds with 10 oxygen (O) atoms (‘Dec’) in a molecule. besides that, it is also known as phosphorus pentoxide.
It can be prepared by heating pure phosphorus with oxygen in blast furnace.
+ →
It is used as a dehydrating agent due to its week van der Waals dispersion forces. Thus, owing to give exothermic reaction when dissolved in watermore precisely, it is a white crystalline anhydrous (without water molecule) solid.
In granular form it can be also used as desiccant as well.
Learn more about phosphorus from the given link:
brainly.com/question/25352398
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<u>Answer:</u> The density of NaCl solution is 3.930 g/mL
<u>Explanation:</u>
We are given:
Mass of cylinder,
= 21.577 g
Mass of NaCl and cylinder combined, M = 39.664 g
Mass of NaCl,
= 
To calculate density of a substance, we use the equation:

We are given:
Mass of NaCl = 18.087 g
Volume of NaCl solution = 4.602 mL
Putting values in above equation, we get:

Hence, the density of NaCl solution is 3.930 g/mL
<span>Answer:
CH3-CH2-0-CH2-CH3
that is diethyl ether
mechanism is SN2</span>