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Brilliant_brown [7]
3 years ago
12

The starting amount of radioactive iodine-131 was 250 g. The half-life is 8 days. When Leslie measured the amount, she measured

15.625 g of radioactive iodine. How many days have elapsed between measurements
Chemistry
1 answer:
love history [14]3 years ago
3 0

Answer:

32 days

Explanation:

Half life is the amount of time it takes to get to half of the starting concentration / amount.

Starting amount = 250 g

Half life = 8 days

Amount left = 15.625 g

How many days ? That is, how many half lives....

After first Half life;

Amount left = 250 / 2 = 125 g

After second half life;

Amount left = 125 / 2 = 62.5 g

After third half life;

Amount left = 62.5 / 2 = 31.25 g

After fourth half life;

Amount left = 31.25 g / 2 = 15.625 g

That is the radioactive iodine - 131 went though four half lives.

How many days = Number of half lives * Half life

How many days = 4 * 8 = 32 days

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4.8 grams of H₂ will be produced if 175g of HCI are allowed to react completely with sodium

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By stoichiometry of the reaction (that is, the relationship between the amount of reagents and products in a chemical reaction) you can see that the following amounts in moles of each compound react and are produced:

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Then, by stoichiometry of the reaction, the following amounts in grams of each of the compounds participating in the reaction react and are produced:

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mass of H_{2} =\frac{175 g of HCl*2g ofH_{2} }{72.9 g of HCl}

mass of H₂= 4.8 g

<u><em>4.8 grams of H₂ will be produced if 175g of HCI are allowed to react completely with sodium</em></u>

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