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Slav-nsk [51]
2 years ago
9

How many mg of a 31-mg sample of calciul 47 remains after 45 days

Chemistry
2 answers:
Feliz [49]2 years ago
8 0
36 days is 8 half-life periods
mario62 [17]2 years ago
7 0
<span>36 days is 8 half-life periods</span>
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How do i make a friend?
Diano4ka-milaya [45]
Ask someone to be your friend. If they dont want to be your friend then ask someone else. 

3 0
3 years ago
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Suppose a new group 5A element is discovered. Photoelectron spectroscopy (PES) reveals that its last two peaks occur at 1370 kJ/
iren2701 [21]

Answer: The average valence electron energy (AVEE) of this element =

1014.2 KJ/ mol  or  1.0142mJ/mol.

Explanation:

The average valence electron energy =  (number of electrons in s subshell  x  Ionization energy of that subshell) + (number of electrons in p subshell  x  Ionization energy of that subshell) / total number of electrons in both subshells of the valence shells.

The 5A elements are non-metals like Nitrogen and Phosphorus with the metallic character increasing as you go down the group, So a new 5A element will have characteristics of its group with 5 valence electron in its outermost shell represented as ns2 np3

Therefore  the average valence electron energy (AVEE) of this element will be calculated as

The average valence electron energy = (2 x 1370  kJ/mol + 3 x 777 kJ/mol.) / 5

2740+2331/ 5 =5071/5

=1014.2 KJ/ mol  or  1.0142mJ/mol.

5 0
3 years ago
How is stoichiometry used to calculate energy released when a mass of liquid freezes?
kati45 [8]

Answer:

D. Grams liquid x mol/g x delta Hf​reezing

Explanation:

Hello there!

In this case, according to the given information, it turns out possible for us to reason that the stoichiometry used to calculate energy released when a mass of liquid freezes, involves the grams of the liquid, the molar mass of the liquid, as given in all the group choices, and the enthalpy of freezing because that is the process whereby a liquid goes solid.

In such a way, we infer that the correct factor would be D. Grams liquid x mol/g x delta Hf​reezing which sometimes is the negative of the enthalpy of fusion as they are contrary processes.

Regards!

6 0
3 years ago
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The Half-Life of Pa-234 is 6.75 hours. How much (what fraction) of a sample of this isotope remains after 20.25 hours?
Grace [21]
So in one hour half the amount remains (that's what half life means). In two hours 1/4 (or half of half) would remain and in three hours 1/8 would remain.
So the answer is 1/8
6 0
2 years ago
A metal, M, forms an oxide compound with the
lapo4ka [179]

Answer:

Group 1

Explanation: because the compound has a formula of M2O , the number of valence electrons of M should be 1.

5 0
3 years ago
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