Chemistry, 17.07.2019 23:00 kcarstensen59070

How many molecules (not moles) of nh3 are produced from 6.89×10−4 g of h2?

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Answer from: davia97

First, let's find the moles of hydrogen used to produce the ammonia
mol = mass ÷ molar mass
if the mass of hydrogen = 6.89 × 10⁻⁴ g
& the molar mass of hydrogen = 2 g/mol
then moles of hydrogen = (6.89 × 10⁻⁴ g) ÷ 2 g/mol
moles of H₂ = 3.445 × 10⁻⁴ mol

Next, balanced eq'n for the production of ammonia from hydrogen gas and nitrogen gas:
N₂ + 3H₂ → 2NH₃

Now, the mole ratio (ratio of the coefficients used to balance the equation) of H₂ : NH₃ is 3 : 2

∴ if the moles of H₂ = 3.445 × 10⁻⁴
then based on the mole ratio, the moles of NH₃ = [(3.445 × 10⁻⁴) ÷ 3] × 2
= (1.14833 × 10⁻⁴) × 2
∴ mole of NH₃ = 2.2967 × 10⁻⁴
Now, # of molecules = moles × Avogadro's Constant

∴ # of molecules of NH₃ = (2.2967 × 10⁻⁴)  × (6.02 × 10²³)
  = 1.383 × 10²⁰ molecules

Thus, the molecules of NH₃ produced is ≈ 1.38 × 10²⁰ molecules.

Answer from: Quest

what are the two models

explanation:

Answer from: Quest

assuming that your periodic table has eighteen columns, you should highlight the four elements in the third column from the left of the table.

explanation

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the $3d$ have energy higher than those in the $4 s$ orbital while lower than those of the $4 p$ orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the $4s$ orbital is therefore filled right after $3p$ orbitals and before $3 d$ orbitals.

potassium has electron configuration $[\text{ar}] 4 s^{1}$ and calcium $[\text{ar}] 4 s^{2}$ . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration $[\text{ar}] 4 s^{2} \; 3d^{1}$ and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the $ns^{2} \; (n-1) p^{1}$ and should be highlighted as well.

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