Answer:
107g
Explanation:
Magnesium fluoride (MgF₂) has a molecular mass of:
Mg: 24,305 g/mol × 1 = 24,305 g/mol
F: 18,998 g/mol × 2 = 37,996 g/mol
MgF₂ = 24,305g/mol + 37,996g/mol = 62,301g/mol. That means the mass of 1,72 mol of MgF₂ is:
1,72 mol F₂ × (62,301g / 1mol) = <em>107g</em>
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Answer:
55g NH₄Cl / 100g Water
Explanation:
Solubility of a substance define the amount of solute per solvent in a saturated solution. The solution can dissolve additional solute if heated.
In the problem, as the first crystal appears at 61°C the solubility in this temperature is the concentration of the solution, that is:
2,75g NH₄Cl / 5,0g water ₓ 100 = <em>55g NH₄Cl / 100g Water</em>
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Answer:
Rank in increasing order of effective nuclear charge:
Explanation:
This explains the meaning of effective nuclear charge, Zeff, how to determine it, and the calculations for a valence electron of each of the five given elements: F, Li, Be, B, and N.
<u>1) Effective nuclear charge definitions</u>
- While the total positive charge of the atom nucleus (Z) is equal to the number of protons, the electrons farther away from the nucleus experience an effective nuclear charge (Zeff) less than the total nuclear charge, due to the fact that electrons in between the nucleus and the outer electrons partially cancel the atraction from the nucleus.
- Such effect on on a valence electron is estimated as the atomic number less the number of electrons closer to the nucleus than the electron whose effective nuclear charge is being determined: Zeff = Z - S.
<u><em>2) Z eff for a F valence electron:</em></u>
- F's atomic number: Z = 9
- Total number of electrons: 9 (same numer of protons)
- Period: 17 (search in the periodic table or do the electron configuration)
- Number of valence electrons: 7 (equal to the last digit of the period's number)
- Number of electrons closer to the nucleus than a valence electron: S = 9 - 7 = 2
- Zeff = Z - S = 9 - 2 = 7
<u><em>3) Z eff for a Li valence eletron:</em></u>
- Li's atomic number: Z = 3
- Total number of electrons: 3 (same number of protons)
- Period: 1 (search on the periodic table or do the electron configuration)
- Number of valence electrons: 1 (equal to the last digit of the period's number)
- Number of electrons closer to the nucleus than a valence electron: S = 3 - 1 = 2
- Z eff = Z - S = 3 - 2 = 1.
<em>4) Z eff for a Be valence eletron:</em>
- Be's atomic number: Z = 4
- Total number of electrons: 4 (same number of protons)
- Period: 2 (search on the periodic table or do the electron configuration)
- Number of valence electrons: 2 (equal to the last digit of the period's number)
- Number of electrons closer to the nucleus than a valence electron: S = 4 - 2 = 2
- Z eff = Z - S = 4 - 2 = 2
<u><em>5) Z eff for a B valence eletron:</em></u>
- B's atomic number: Z = 5
- Total number of electrons: 5 (same number of protons)
- Period: 13 (search on the periodic table or do the electron configuration)
- Number of valence electrons: 3 (equal to the last digit of the period's number)
- Number of electrons closer to the nucleus than a valence electron: S = 5 - 3 = 2
- Z eff = Z - S = 5 - 2 = 3
<u><em>6) Z eff for a N valence eletron:</em></u>
- N's atomic number: Z = 7
- Total number of electrons: 7 (same number of protons)
- Period: 15 (search on the periodic table or do the electron configuration)
- Number of valence electrons: 5 (equal to the last digit of the period's number)
- Number of electrons closer to the nucleus than a valence electron: S = 7 - 5 = 2
- Z eff = Z - S = 7 - 2 = 5
<u><em>7) Summary (order):</em></u>
Atom Zeff for a valence electron
- <u>Conclusion</u>: the order is Li < Be < B < N < F
30.6 g of AgNO₃
Explanation:
We have the following chemical reaction:
Na₃PO₄ + 3 AgNO₃ → Ag₃PO₄ + 3 NaNO₃
Now we calculate the number of moles of Na₃PO₄:
number of moles = mass / molecular weight
number of moles of Na₃PO₄ = 9.44 / 164 = 0.06 moles
Now we formulate the following reasoning:
if 1 mole of Na₃PO₄ will react with 3 moles of AgNO₃
then 0.06 moles of Na₃PO₄ will react with X moles of AgNO₃
X = (0.06 × 3) / 1 = 0.18 moles of AgNO₃
mass = number of moles × molecular weight
mass of AgNO₃ = 0.18 × 170 = 30.6 g
Learn more about:
mole concept
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Answer:
The mass number (A) of an atom is the total number of protons and neutrons in its nucleus. ... Because electrons have virtually no mass, just about all the mass of an atom is in its protons and neutrons. Therefore, the total number of protons and neutrons in an atom determines its mass in atomic mass units (Table 4.5. 1).
