In the physical properties, it is mentioned that the element has 4 valence electrons. The elements in the periodic table are arranged such that, the number of valence electrons present in the neutral atoms belonging to a particular group is equal to the group number.
Thus, the unidentified element can be best classified as a nonmetal in period 4
Ans C)
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Answer:
3.18 (w/w) %
Explanation:
In the problem, you can find mass of NaClO knowing the reaction of NaClO with Na₂S₂O₃ is:
NaClO + 2Na₂S₂O₃ + H₂O → NaCl + Na₂S₄O₆ +2NaOH + NaCl
<em>Where 1 mole of NaClO reacts with 2 moles of Na₂S₂O₃</em>
<em> </em>Moles of thiosulfate in the titration are:
0.0101L ₓ (0.042mol / L) = 4.242x10⁻⁴ moles of Na₂S₂O₃
Thus, moles of NaClO in the initial solution are:
4.242x10⁻⁴ moles of Na₂S₂O₃ ₓ (1mol NaClO / 2 mol Na₂S₂O₃) = 2.121x10⁻⁴ moles NaClO
As molar mass of NaClO is 74.44g/mol, mass of 2.121x10⁻⁴ moles are:
2.121x10⁻⁴ moles ₓ (74.44g / mol) = <em>0.0158g of NaClO</em>
As mass of bleach is 0.496g, mass percent is:
0.0158g NaClO / 0.496g bleach ₓ 100 =
<h3>3.18 (w/w) % </h3>
Answer:
The heat of formation = Heat of formation of the products - Heat of formation of the reactants
= -2323 + 104 = -2219 ≈ -2218.6 kJ/mol.
Explanation:
The law of conservation of energy states that the total energy is constant in any process. Energy may change in form or be transferred from one system to another, but the total remains the same
The heat of formation of C₃H₈ is 3C + 4 H₂ → C₃H₈
-104 kJ/mol
The heat of formation of O₂ is O₂ (g) → O₂ (g)
0 kJ/mol
The heat of formation of H₂O is H₂(g) + 1/2 O₂→ H₂O (g)
-286kJ/mol
The heat of formation of CO₂ is C (s) + O₂ (g) → CO₂ (g)
-393 kJ/mol
Therefore, in the given reaction we have;
C₃H₈ + 4 O₂ → 3 CO₂ + 4 H₂O
The heat of formation = Heat of formation of the products - Heat of formation of the reactants
The heat of formation = 3 × (-393) + 4 × (-286) - (-104) = -2219 ≈ -2218.6 kJ/mol.