For each of the following unbalanced reactions, sup- pose exactly 5.00 g of each reactant is taken. Deter- mine which reactant i
1 answer:
Answer:
The reactant that is limiting is the Na2B4O7, and the mass of the excess reagent (H2SO4) is 2.5627g.
Explanation:
The unbalanced reaction is:
Na2B4O7 + H2SO4 + H2O ⇒ H3BO3 + Na2SO4
- First the equation is balanced
Na2B4O7 + H2SO4 + 5H2O ⇒ 4H3BO3 + Na2SO4
According to the balanced equation we observe that it takes 1 mol of Na2B4O7 to react with 1 mol of H2SO4.
- Then the molecular weights of each reactant are determined:
MWNa2B4O7 = 201.197 g/mol
MWH2SO4 = 98.075 g/mol
- It is calculated how many moles will react with 5 initial grams of each.
201.197 g of Na2B4O7 ⇒ 1 mol
5 g ⇒ X
of Na2B4O7
98.075 g of H2SO4 ⇒ 1 mol
5 g ⇒ X
of H2SO4
The limiting reagent is the one that is consumed first, in this case it is Na2B4O7, since 0.02485 moles are needed for both reactants, then there are 0.02613 moles of H2SO4 left over. With these moles the grams of excess reagent are calculated.
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Since molarity (M) is measured in mols÷L, you will need to convert the units first.
Then, convert 160g of ammonium nitrate into mols using the molar mass 80.043g/mol.
160g ÷ 80.043g/mol = 2.0 mols.
Finally divide the mols by liters.
2.0mols ÷ 2.5L = .80M
Then, convert 160g of ammonium nitrate into mols using the molar mass 80.043g/mol.
160g ÷ 80.043g/mol = 2.0 mols.
Finally divide the mols by liters.
2.0mols ÷ 2.5L = .80M
Answer:
The Work Function is 4.74eV.
Explanation:
The photoelectric effect is a phenomenon in which a beam of light is projected towards a metal plate and this leads to the ejection of electrons from the metal. The minimum amount of energy required for this ejection of electrons is known as the work function. When the energy of the light beam is less than the work function, then the electrons are not emitted.
The photoelectric effect is represented by the equation:
E = φ + KE where
E = energy of the incident photons
KE = kinetic energy of photoelectrons
φ = Work function of the metal
This can also be written in terms of frequency as:
h = h₀ + mv²
= frequency of the incident light beam
₀ = frequency of the photoelectrons
m = mass of the electron
v = velocity of the electron
h = Plank's constant 6.623 x 10⁻³⁴Js
Conversion factor: 1eV = 1.602 x 10⁻¹⁹ J
So, 1.05eV = 1.682 10⁻¹⁹ J
Using the formulas,
(6.623 x 10⁻³⁴Js)(1.40x10¹⁵ s⁻¹) = φ + 1.682 x 10⁻¹⁹ J
(9.272 x 10⁻¹⁹) - (1.682 x 10⁻¹⁹) = φ
φ = 7.590 x 10⁻¹⁹ J = 4.74 eV
Learn more about work function here:
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