The half life of Po-218 is three minutes. How much of a 200 atom sample will remain after 15 minutes

Chemistry

1 answer:

MakcuM [25]3 years ago

6 0

<h3>Answer:</h3>

6.25 atoms

<h3>Explanation:</h3>

<u>We are given</u>;

The half life of Po-218 is 3 minutes

Initial sample is 200 atom
Time of decay is 15 minutes

We are required to calculate the remaining mass after decay;

Half life refers to the time taken for original amount of a radioactive sample to decay to a half.

To calculate the remaining mass we use the formula;

N = N₀ × 0.5^n where n is the number of half lives, N is the new amount and N₀ is the original amount.

n = 15 min ÷ 3 min

= 5

Therefore;

New amount = 200 atom × 0.5^5

= 6.25 atoms

Therefore; the amount of the sample that will remain after 15 minutes is 6.25 atoms.

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Sample A: 300 mL of 1M sodium chloride

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Answer:

sample B contains the larger density

Explanation:

Given;

volume of sample A, V = 300 mL = 0.3 L

Molarity of sample A, C = 1 M

volume of sample B, V = 145 mL = 0.145 L

Molarity of sample B, C = 1.5 M

molecular mass of sodium chloride, Nacl = 23 + 35.5 = 58.5 g/mol

Molarity is given as;

$C = \frac{moles \ of \ solute, \ mol}{liters \ of \ solvent} \\\\Moles \ of \ solute \ for \ sample \ A = 1 \times 0.3 = 0.3 \ mol\\\\Moles \ of \ solute \ for \ sample \ B = 1.5 \times 0.145 = 0.2175 \ mol$