Answer:
B. - 210 kJ
Explanation:
<em>∵ ΔHrxn = ∑(bond energies)products - ∑(bond energies)reactants.</em>
- The bond formation in the products releases energy (exothermic).
- The bond breaking in the reactants requires energy (endothermic).
The products:
- H₂O contains 2 O-H (- 459 kJ/mol) bonds.
- O₂ contain 1 O=O (- 494 kJ/mol) bond.
The reactants:
- H₂O₂ contain 2 O–H (459 kJ/mol) bonds and 1 O–O (142 kJ/mol) bond.
∵ ΔHrxn = ∑(bond energies)products - ∑(bond energies)reactants.
<em>∴ ΔHrxn = [2 (2 x (O–H bond energy) + (1 x (O=O bond energy)] - 2 [(2 x (O–H bond energy) + (1 x (O–O bond energy)] </em>= [2 (2 x - 459 kJ/mol) + (1 x - 494 kJ/mol)] - 2 [(2 x 459 kJ/mol) + (1 x 142 kJ/mol)] = (- 2330 kJ) + (2120 kJ) = <em>- 210 kJ.</em>
Given ,
Mass of sample of cobalt = 27 g
density of sample of cobalt = 9g/cm^3
We know that ,
Density = mass of sample/volume of sample
From that relation ,
We can deduce the following as
Volume = mass of sample/density of sample
Hence , required volume of sample of cobalt = 27 g /9 g/cm^3 = 3 cm^3
The volume is
M/V=D
40.5/15=2.7
The density of the block of aluminum is 2.7 g/cm³.
The molar mass is 286.94 g/mol
The process by which a particular substance or different substances are transformed to another is called as Chemical Reaction. In a chemical reaction the starting compounds which are being reacted with each other are called as Reactants. While, those compounds which are being formed and produced from reactants after reaction are called as Products.
The concentration of reactants decreases as the reaction proceeds and at last their concentration comes to an end. Hence, the reaction stops too. If two reactants are being reacted, then the reactant which is in limited amount will consume first and will result in the termination of reaction.
