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ale4655 [162]
3 years ago
14

If the half-life of a radioisotope is 20,000 years, then a sample in which three-quarters of that radioisotope has decayed is __

_________ years old
Chemistry
1 answer:
poizon [28]3 years ago
4 0
25% remaining = 40,000 years old
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Calculate (a) the pH of a 0.0250 M solution of phenylacetic acid, and (b) the pH of a 0.0500 M solution of sodium phenylacetate.
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A gold coin contains 3.47 × 10^23<br> gold atoms.<br> What is the mass of the coin in grams?
VashaNatasha [74]

Answer:

Mass = 114.26 g

Explanation:

Given data:

Number of gold atoms = 3.47×10²³ atoms

Mass in gram = ?

Solution:

The given problem will solve by using Avogadro number.

It is the number of atoms , ions and molecules in one gram atom of element, one gram molecules of compound and one gram ions of a substance.  The number 6.022 × 10²³ is called Avogadro number.

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In the formula 4H20, how many total hydrogen (H) atoms are there?
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