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mario62 [17]
3 years ago
8

Be sure to answer all parts. Fluoride ion is poisonous in relatively low amounts: 0.2 g of F− per 70 kg of body weight can cause

death. Nevertheless, in order to prevent tooth decay, F− ions are added to drinking water at a concentration of 1 mg of F− ion per L of water. How many liters of fluoridated drinking water would a 70−kg person have to consume in one day to reach this toxic level?
Chemistry
1 answer:
Stells [14]3 years ago
7 0

Answer:

200 liters of fluoridated drinking water would have to be consumed by as person to reach the toxic level.

Explanation:

Toxic level of fluoride ions = 0.2 g per 70 kg body weight

Concentration of fluoride ions in drinking water = 1 mg/ L = 0.001 g/L

1 mg = 0.001 g

Let the volume of drinking water consumed by person to reach the toxic level of fluoride concentration be V.

For 70 kg body weight 0.2 grams of fluoride ions will be toxic.

V\times 0.001 g/L=0.2 g

V=\frac{0.2 g}{0.001 g/L}=200 L

200 liters of fluoridated drinking water would have to be consumed by as person to reach the toxic level.

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Rank the following elements by effective nuclear charge, Zeff, for a valence electron. F LI Be B N
Stels [109]

Answer:

Rank in increasing order of effective nuclear charge:

  • Li < Be < B < N < F

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

  • F                   7
  • Li                   1
  • Be                 2
  • B                   3
  • N                   5

  • <u>Conclusion</u>: the order is Li < Be < B < N < F
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3 years ago
What causes the difference in bond angles in carbon dioxide and water?
egoroff_w [7]

Answer is: C) the fact that the number of lone pairs of electrons on the central atom is greater in the case of water.

Carbon(IV) oxide is nonpolar because CO₂ is linear molecule and the oxygen atoms are symmetrical (bond angles 180°).

Water is polar because of the bent shape of the molecule.

Oxygen atom in water molecule has sp3 hybridization. The bond angle between the two hydrogen atoms is approximately 104.45°.

Oxygen atom has atomic number 8, it means it has eight protons and eight electrons, so atom has neutral charge. Oxygen is a nonmetal.

Electron configuration of oxygen atom: ₈O 1s² 2s² 2p⁴.

Oxygen atom has six valence electrons , two lone pairs and two electrons that form two sigma bonds with hydrogen atoms.

Carbon is a chemical element with symbol C and atomic number 6, which means it has 6 protons and six electrons. Four valence electrons are in 2s and 2p orbitals.  

Electron configuration of carbon atom: ₆C 1s² 2s² 2p².  

In carbon dioxide, carban has sp hybridization with no lone pairs.

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How many protons are in oxygen's nucleus?
UkoKoshka [18]
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Use the following information to answer the following question.
Irina-Kira [14]

Answer:

For these problems, we need to compare the theoretical yield that we'd get from performing stoichiometry to the actual yield stated in the problem. % yield is the actual yield/theoretical yield x 100%  

Cu + 2 AgNO₠→ Cu(NOâ‚)â‚‚ + 2 Ag ==> each mole of copper yields two moles of silver  

12.7-g Cu x ( 1 mol Cu /63.5-g Cu) x ( 2 mol Ag / 1 mol Cu) x (108-g Ag / 1 mol Ag) = 43.2-g Ag. This is the theoretical yield. Now, since we got 38.1-g Ag our % yield is:  

38.1-g/43.2-g x 100% = 88.2%

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2 years ago
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