A 0.784 g sample of magnesium is added to a 250 ml flask and dissolved in 150 ml of water. magnesium hydroxide obtained from the
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Answer:
Explanation:
This scenario is unrealistic since Al(OH)₃ is not soluble in water.
The question consists of two parts:
A. Stoichiometry — where we determine volumes, masses, and moles for the products
B. Calorimetry — where we assess the enthalpy of the reaction.
A. Stoichiometry
1. Determine the volume of Al(OH)₃
(a) The balanced chemical equation:
2Al(OH)₃ + 3H₂SO₄ ⟶ Al₂(SO₄)₃ + 6H₂O
M/V: 66.667
c/mol·L⁻¹: 4.000 3.000
(b) Moles of H₂SO₄
(c) Moles of Al(OH)₃
The molar ratio stands at 2 mmol Al(OH)₃: 3 mmol H₂SO₄
(d) Volume of Al(OH)₃
B. Calorimetry
This reaction has two energy exchanges.
q₁ = heat from the reaction
q₂ = heat used to heat the calorimeter
q₁ + q₂ = 0
nΔH + mCΔT = 0
Data:
Moles of Al₂(SO₄)₃ = 0.066 667 mol
C = 1.10 J°C⁻¹g⁻¹
T_initial = 22.3 °C
T_final = 24.7 °C
Calculations
(a) Mass of solution
Assume solutions are as dense as water (though not realistic).
Mass of sulfuric acid solution = 66.667 g
Mass of aluminium hydroxide solution = 50.000
TOTAL = 116.667 g
(b) ΔT
ΔT = T_final - T_initial = 24.7 °C - 22.3 °C = 2.4°C
(c) ΔH
This result appears nonsensical, but it is derived from your given figures.
Answer: The percentage abundance for isotope is 3.09 %.
Explanation:
The average atomic mass of an element is calculated by taking the sum of the masses of all isotopes weighted by their respective natural fractional abundances.
To compute average atomic mass, the following formula is applied:
.....(1)
From the information provided:
Let the fractional abundance for isotope be 'x'
- For
isotope:
Mass of isotope = 27.9769 amu
Percentage abundance of isotope = 92.22 %
Fractional abundance for isotope = 0.9222
- For
isotope:
Mass of isotope = 28.9764 amu
Percentage abundance for isotope = 4.68%
Fractional abundance of isotope = 0.0468
- For
isotope:
Mass of isotope = 29.9737 amu
Fractional abundance for isotope = x
- The average atomic mass of silicon is 28.084 amu
By inserting these values into equation 1, we derive:
To convert this fractional abundance into a percentage, multiply by 100:
This shows that the percentage abundance for isotope is 3.09 %.