You can demonstrate that a piece of chalk has mass by putting it on a pan scale. Pan scales determine mass in grams. Also if the mass feels like it has some weight to it (although not to be confused with weight, they are two different things!), it most likely has mass.
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Answer:

Explanation:
Hello there!
In this case, since the radioactive decay is considered as first-order kinetic model, whereby the remaining mass of the radioactive material involves the initial one, the rate constant and elapsed time:

As we were not initially given the rate constant, we can use the half-life to calculate it as follows:

Thus, we can calculated the elapsed time for the given conditions to obtain:

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Answer:
Option B. Heptane
Explanation:
To obtain the parent name of the above compound, all we need to do is to locate the longest continuous carbon chain.
The longest continuous carbon chain of the above compound is 7.
Next, we shall also consider the chain if there is any double or triple bond.
From the diagram given above, no double or triple bond is present.
Finally, the parent name of the compound is heptane since the longest continuous carbon chain is 7 and no double or triple bond is present in the compound.