Nitrogen (N2) and hydrogen (H2) gases react to form ammonia, which requires -99.4 J/K of standard entropy (ΔS°).
What is standard entropy?
The difference between the total standard entropies of the reaction mixture and the summation of the standard entropies of the outputs is the standard entropy change. Each entropy in the balanced equation needs to be compounded by its coefficient, as shown by the letter "n."
Calculation:
Balancing the given reaction following-
1/2 N₂(g) + 3/2 H₂ (g)→ NH₃ (g)
ΔS° = [1 mol x S° (NH₃)g] - [1/2 mol x S° (N₂)g] - [3/2 mol x S°(H₂)g]
Here S° = standard entropy of the system
Insert into the aforementioned equation all the typical entropy values found in the literature:
ΔS° = [1 mol x 192.45 J/mol.K] - [1/2 mol x 191.61 J/mol.K] - [3/2 mol x 130.684 J/mol.K]
⇒ΔS° = - 99.4 J/K
Therefore, the standard entropy, ΔS° is -99.4 J/K.
Learn more about standard entropy here:
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Make a quick chart with each element represented, and count them up. HINT - leave the polyatomic anions together - in this case, PO4
Left Right
1 Ca 3
2 O 1
5 H 2
1 PO4 2
Begin by balancing like finding common denominators of fractions - apply to both sides:
I started by adding a 2 in front of H3PO4 on the left, them 6 in front of H2O on the right. Last, a 3 in front of Ca (OH)2. Then, re-count using the chart format to make sure you're right.
3Ca(OH)2 + 2H3PO4 = Ca3(PO4)2 + 6H2O
Answer:
3.51× 10²³ formula units
Explanation:
Given data:
Mass of CaO = 32.7 g
Number of formula units = ?
Solution:
First of all we will calculate the number of moles.
Number of moles = mass/molar mass
Number of moles = 32.7 g/ 56.1 g/mol
Number of moles = 0.583 mol
Number of formula units:
1 mole = 6.022 × 10²³ formula units
0.583 mol × 6.022 × 10²³ formula units / 1 mol
3.51× 10²³ formula units
The number 6.022 × 10²³ is called Avogadro number.
To determine mass of the given number of atoms of mercury, we need a factor that would relate the number of atoms to number of moles. In this case, we use the Avogadro's number. It is a <span>number that represents the
number of units in one mole of any substance. This has the value of 6.022 x
10^23 units / mole. The number of units could be atoms, molecules, ions or electrons. To convert into mass, we use the given amu of mercury since it is equal to grams per mole. We calculate as follows:
</span>3.0 x 10^10 atoms ( 1 mol / 6.022 x 10^23 atoms ) ( 200.59 g / 1 mol ) = 9.99x10^-12 g Hg
