Answer:
Choice number two. The value of "X" in this equation should be constant for all elements across a period.
Explanation:
Electrons are negative while protons are positive. Electrons are attracted to the proton but repel each other.
Consider an atom where electrons occupy more than one energy level. Consider the Bohr Model for that atom. Protons in the nucleus attract the electrons towards the center of the atom. However, at the same time, electrons in the inner shell will repel the valence electrons. That creates an outward force that pushes the valence electrons away from the atom.
The two forces mostly balance each other, but the attraction is slightly stronger. As a result, the overall force on the valence electrons is attractive. The effective nuclear charge gives the number of protons required to produce an attraction of that strength if there was no repulsion at all.
The value of effective nuclear charge is approximately the same as atomic number minus the number of inner-shell electrons. Apparently, the "X" in this question stands for the number of inner-shell electrons.
By the Aufbau Principle, all spots in the inner shell must be filled before more electrons can be added. Additionally, atoms in the same period have the same number of inner shells. As a result, the number of inner-shell electrons will be the same for all atoms in each period. Hence, the value of "X" should stay (approximately) the same across each period.
Answer:
C6H12O6.
Explanation:
Adding up the relative atomic masses of the elements
C + 2H + O
= 12 + 2*1 + 16.
= 30.
180 / 30 = 6 so the molecular formula is:
C6H12O6.
Answer:
the mass of 8.03 mole of NH3 is 136.51 g
Explanation:
The computation of the mass is shown below:
As we know that
Mass = number of moles × molar mass
= 8.03 mol × 17 g/mol
= 136.51 g
Hence, the mass of 8.03 mole of NH3 is 136.51 g
We simply multiplied the number of moles with the molar mass so that the mass could come
Answer:
Mass ratio: 71:112
Atomic ratio: 2:7
Explanation:
1. To get the mass ratio of of the compound Cl2O7, the following steps are followed:
- The atomic mass of Cl = 35.5g/mol, O = 16g/mol
- The mass of each element in the compound is as follows:
Cl2 = 35.5(2) = 71g
O7 = 16(7) = 112g
The mass ratio is the ratio of one mass of an element to another in the compound, hence, the mass ratio is 71:112
- The molar mass of the compound, Cl2O7, is determined:
71 + 112 = 183g/mol
- The mass percent of each element is determined by dividing the mass of each element present by the Molar Mass:
Cl = 71/183 = 0.3879 × 100 = 38.8%
O = 112/183 = 0.612 × 100 = 61.2%
2. Atomic ratio is the ratio of one atom in a molecule to another. It can be calculated this:
In Cl2O7, there are 9 total atoms (2 atoms of Cl + 7 atoms of oxygen).
Hence, that atomic ratio of Cl to oxygen in Cl2O7 is 2:7
The provided information are:
volume of 0.85 M lactic acid = 225 ml
volume of 0.68 M sodium lactate = 435 ml
Ka of the lactate buffer = 1.38 x 10⁻⁴
The equation for dissociation of lactic acid is:
CH₃CH(OH)COOH(aq) + H₂O ⇄ CH₃CH(OH)COO⁻(aq) + H₃O⁺(aq)
The pH of buffer is calculated from Henderson-Hasselbalch equation, which is:
pH = pKa + log
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pKa = - log Ka = - log (1.38 x 10⁻⁴) = 3.86
The number of moles of lactic acid and lactate are as follows:
n (Lactic acid) = 225 ml x 0.85 mmol/ml = 191.25 mmol
n (Lactate) = 435 ml x 0.68 mmol/ml = 295.8 mmol
The number of moles of lactic acid and lactate in total volume of the solution:
[CH₃CH(OH)COOH] = n (lactic acid) / 660 ml = 191.25 mmol / 660 ml = 0.29 M
[CH₃CH(OH)COO⁻] = n (lactate) / 660 ml = 0.45 M
pH = 3.86 + log
= 3.86 + 0.191 = 4.05
So the pH of given solution is 4.05
