A 50.0 g sample of an unknown substance, initially at 20.2 °C, was heated with 1.55 kJ of energy. The final temperature of the s
1 answer:
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Answer:
The mass of oxygen that reacted is approximately 1.6 grams of oxygen
Explanation:
The given information are;
The mass of magnesium in the reaction = 2.43 grams
The final mass of the magnesium oxide = 4.12 grams
The chemical equation for the reaction is given as follows;
2Mg + O₂ → 2MgO
From which we see that two moles of magnesium, Mg, reacts with one mole of oxygen gas molecule, O₂, to produce two moles of magnesium oxide, MgO
The number of moles of magnesium present, , is given as follows;
By the given chemical equation, 2 moles of magnesium reacts with one mole of O₂, therefore;
1 mole of magnesium will react with 1/2 moles of oxygen which is 0.5 moles of oxygen also;
0.1 mole of magnesium will react with 0.05 moles of oxygen
The mass of one mole of oxygen = The molar mass of oxygen = 32 g/mol
The mass of oxygen in the reaction = The number of moles of oxygen × The molar mass of oxygen
The mass of oxygen in the reaction = 0.05 × 32 = 1.6 grams
Also from the molar mass of MgO which is 40.3044 g/mol, we have;
The mass fraction of oxygen = 16/40.3044 = 0.39698 ≈ 0.4
The mass of oxygen = 0.39698 × 4.12 = 1.636 g
Therefore, the mass of oxygen in the reaction is approximately 1.6 grams.
Answer:
pH before addition of KOH = 4.03
pH after addition of 25 ml KOH = 7.40
pH after addition of 30 ml KOH = 7.57
pH after addition of 40 ml KOH = 8.00
pH after addition of 50 ml KOH = 10.22
pH after addition 0f 60 ml KOH = 12.3
Explanation:
pH of each case in the titration given below
(6) After addition of 60 ml KOH
Since addition of 10 ml extra KOH is added after netralisation point.
Concentration of solution after addition 60 ml KOH is calculated by
M₁V₁ = M₂V₂
or, 0.23 x 10 = (50 + 60)ml x M₂
or M₂ = 0.03 Molar
so, concentration of KOH = 0.03 molar
[OH⁻] = 0.03 molar
pOH = 0.657
pH = 14 - 0.657 = 13.34
