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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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The net ionic equation for formation of an aqueous solution of nii2 accompanied by evolution of co2 gas via mixing solid nico3 a
Ann [662]

Answer:

NiCO3 (s) + 2H+ (aq) → H2O (l) + CO2 (g) + Ni2+ (aq)

Explanation:

To write the complete ionic equation:

1. Start with a balanced molecular equation.

2. Break all soluble strong electrolytes (compounds with (aq) beside them) into their ions

3. indicate the correct formula and charge of each ion

4. indicate the correct number of each ion

5. write (aq) after each ion

6. Bring down all compounds with (s), (l), or (g) unchanged.

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3 years ago
Give an example of a chemical reaction during which a single substance breaks<br> down. *
RoseWind [281]

Answer:

2NaCl(l) => 2Na(s) + Cl₂(g)

Explanation:

Electrolysis of melt NaCl to form sodium (Na) metal and chlorine (Cl₂) gas.

This is a class of reaction called 'Decomposition Rxns'. For what it's worth, there are 6 distinct compound types that undergo breakdown by decomposition. The acronym C O A C H E can help remember them.

C - Carbonates => CaCO₃(s) => CaO + CO₂

O - Oxides of Metals => 2Fe₂O₃(s) => 4Fe°(s) + 3O₂(g)

A - Acids (Oxoacids) => H₂CO₃(aq) => CO₂(g) + H₂O(l)

C - Chlorates, Bromates & Iodates => 2KClO₃(s) => 2KCl(s) + 3O₂(g)

H - Hydroxides => Ca(OH)₂(s) => CaO(s) + H₂O(l)

E - Electrolysis => see above electrolysis of NaCl(l)

6 0
3 years ago
7. DNA is essential to living organisms because it O is a spiral helix can prevent disease O carries the genetic code O can brea
dsp73

Answer: DNA is essential...because it carries the genetic code.

Explanation:

Although the other statements are true about DNA, it's a spiral helix and can break apart, its main function is that it contains the genetic code for organisms.

5 0
3 years ago
Question 9 (5 points)
frozen [14]

Answer:

A. air pressure,this is answer.

5 0
3 years ago
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Nijar did an experiment to test a hypothesis that baking soda is just as effective a cleaner as bleach. He found this not to be
kow [346]

Answer:

b no

Explanation:

4 0
3 years ago
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