Answer:
The limiting reactant is the Salicylic acid (C₇H₆O₃)
Explanation:
In order to find the limting reactant or the excess reactant of a chemical reaction we have to compare the moles of each reactant to the stoichiometry of the reaction; we usually make rules of three.
First of all we need to convert the mass of the reactants, to moles:
70 g / 138 g/mol = 0.507 moles of salicylic acid
80g / 102 g/mol = 0.784 moles of acetic anhydride
The reaction is: 2C₇H₆O₃ (aq) + C₄H₆O₃(aq) → 2C₉H₈O₄(aq) + H₂O(l)
Ratio is 2:1.
2 moles of salicylic acid need 1 mol of acetic anhydride to react
Then, 0.507 moles of salicylic will react with (0.507 . 1) / 2 = 0.254 moles of acetic anhydride (It's ok, I have 0.784 moles and I only need 0.254 moles, so acetic anhydride still remains, the C₄H₆O₃ is the excess reactant)
In conclussion, the limiting reactant is the Salicylic acid (C₇H₆O₃)
Let's verify: 1 mol of anhyride needs 2 moles of salicylic acid
Therefore, 0.784 moles of anhydride will react with (0.784 . 2) /1 = 1.57 moles. → We do not have enough C₇H₆O₃, we have 0.507 moles but we need 1.57.
I think so, <span> how much of all chemistry is to do with numbers? A lot! So being good at mathematics makes a huge aspect of chemistry so much easier but if you aren't mathematical then you can work at it and become reasonably proficient at it.</span>
Answer:
When magma reaches the surface, its dissolved gas content increases is true
<u>Explanation</u>:
The volcanic eruptions happen because of magma that is expelled on the earth’s surface. At the earth’s depth, all magma have gas dissolved in liquid. When the pressure has decreased the magma rises towards the earth’s surface creating a separate vapour phase.
As pressure reduces the volume of gas will expands and giving magma its 'explosive character'. Thus, as magma reaches the surface the dissolved gas content decreases and magma comes out of earth’s surface.
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
