Which expression represents the mass of sodium remaining after h half-lives?

S = 0.5(800)h

S = 800(0.5)h

S = 8000.5h
S = 800h + 0.5

1 answer

To determine the expression that represents the mass of sodium remaining after \( h \) half-lives, we can use the concept of half-life.

The mass remaining after \( h \) half-lives can be calculated using the formula:

\[ S = S_0 \left(0.5\right)^h \]

where:

  • \( S_0 \) is the initial mass,
  • \( h \) is the number of half-lives,
  • \( S \) is the remaining mass after \( h \) half-lives.

If we assume the initial mass \( S_0 \) is 800 (which seems to be suggested by the options provided), the formula becomes:

\[ S = 800 \left(0.5\right)^h \]

Now let's check the options:

  1. \( S = 0.5(800)h \) - This is not correct as it does not represent the exponential decay.
  2. \( S = 800(0.5)^h \) - This matches our derived formula. This is the correct expression.
  3. \( S = 8000.5h \) - This is not correct as it also does not represent the exponential decay.
  4. \( S = 800h + 0.5 \) - This is not correct as it is a linear equation, not an exponential decay.

Thus, the correct expression that represents the mass of sodium remaining after \( h \) half-lives is:

\( S = 800(0.5)^h \).

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