The correct answer is 12.2% BaO.
The solution is found by dividing the mass of the BaO, which is 25.8 grams, by the total mass of the solution, which is 212 grams, then multiplying it by 100 to get the percentage:
Answer:
The number of moles of benzaldehyde = 0.0253 moles
Explanation:
The molecular formula of benzaldehyde is C₇H₆O
Its molecular mass is calculated from the atomic masses of the constituent atoms.
C = 12.0 g: H = 1.0 g; O = 16.0 g
Molecular mass = ( 12 * 7) + (1 * 6) + (16 * 1) = 106.0 g/mol
Number of moles of substance = mass of substance/ molar mass of the substance
mass of benzaldehyde = 2.68; molar mass = 106.0 g/mol
Number of moles of benzaldehyde = 2.68 g/ 106 g/mol = 0.0253 moles
Therefore, the number of moles of benzaldehyde = 0.0253 moles
Since the density of water is 1 g /mL, hence there is 100
g of H2O. So total mass is:
m = 100 g + 5 g = 105 g
=> The heat of reaction can be calculated using the
formula:
δhrxn = m C ΔT
where m is mass, C is heap capacity and ΔT is change in
temperature = negative since there is a decrease
δhrxn = 105 g * 4.18 J/g°C * (-2.30°C)
δhrxn = -1,009.47 J
=> However this is still in units of J, so calculate
the number of moles of NaCl.
moles NaCl = 5 g / (58.44 g / mol)
moles NaCl = 0.0856 mol
=> So the heat of reaction per mole is:
δhrxn = -1,009.47 J / 0.0856 mol
δhrxn = -11,798.69 J/mol = -11.8 kJ/mol
