Answer:
Na₂CO₃.2H₂O
Explanation:
For the hydrated compound, let us denote is by Na₂CO₃.xH₂O
The unknown is the value of x which is the amount of water of crystallisation.
Given values:
Starting mass of hydrate i.e Na₂CO₃.xH₂O = 4.31g
Mass after heating (Na₂CO₃) = 3.22g
Mass of the water of crystallisation = (4.31-3.22)g = 1.09g
To determine the integer x, we find the number of moles of the anhydrous Na₂CO₃ and that of the water of crystallisation:
Number of moles = 
Molar mass of Na₂CO₃ =[(23x2) + 12 + (16x3)] = 106gmol⁻¹
Molar mass of H₂O = [(1x2) + (16)] = 18gmol⁻¹
Number of moles of Na₂CO₃ = 
= 0.03mole
Number of moles of H₂O = 
= 0.06mole
From the obtained number of moles:
Na₂CO₃ H₂O
0.03 0.06
Simplest
Ratio 0.03/0.03 0.03/0.06
1 2
Therefore, x = 2
Answer:
See below.
Explanation:
The mass of octane in the sample of gasoline is 0.02851 * 482.6 = 13.759 g of octane.
The balanced equation is:
2C8H18(l) + 25O2(g) ----> 16CO2(g) + 18H2O(g)
From the equation, using atomic masses:
228.29 g of octane forms 704 g of CO2 and 324.3 g of H2O
So the mass of CO2 formed from the combustion of 13.759 g of octane = (704 * 13.759) / 228.29
= 42.43 g of CO2.
Amount of water = 324.3 * 13.759) / 228.29
= 19.55 g of H2O.
The chemical formula for calcium hydroxide is Ca(OH)₂ and that of nitric acid is HNO₃. By these chemical formula it can be deduced that the number of equivalents per mole of Ca(OH)₂ is 2 because of 2 OH⁻ and for HNO₃ is 1 because of H⁺.
For the neutralization reaction, the number of equivalents should be equal.
V₁n₁ = V₂n₂
Substituting the known values and with the incorporation of the concept above,
(V₁)(0.0250 mol/L)(2 equivalents/mol) = (33.50 mL)(0.020 mol/L)(1 equivalent/mol)
V₁ = 13.4 mL
Hence, the volume of calcium hydroxide needed is approximately equal to 13.4 mL.
Answer:
The presence of hydrogen ions
Explanation:
Nitric acid is formed when hydrogen ions combine with nitrogen oxide ions leading to formation of a strong acid. Wheareas for strong bases the hydroxyl iins must be present, for strong acid, the hydrogen ions contribute to the acidity. Therefore, from the formula of nitric acid, it has hydrogen ions, an indicator of a strong acid.
