Answer:
175 kJ
Explanation:
Activation energy can be defined as the potential energy that is needed to change reactants to products. This is the minimum energy required for the chemical reaction to take place. Thus, using the given figure:
Activation energy = activation complex - reactant energy
In the given figure, activation complex = 400 kJ
reactant energy = 225 kJ
Therefore:
Activation energy = 400 - 225 = 175 kJ
H2(g) +C2H4(g)→C2H6(g)
H-H +H2C =CH2→H3C-Ch3
2C -H bonds and one C-C bond are formed while enthalpy change (dH) of the reaction,
H-H: 432kJ/mol
C=C: 614kJ/mol
C-C: 413 kJ/mol
C-C: 347 kJ/mol
dH is equal to sum of the energies released during the formation of new bonds or negative sign, and sum of energies required to break old bonds or positive sign.
The bond which breaks energy is positive.
432+614 =1046kJ/mol
Formation of bond energy is negative
2(413) + 347 = 1173 kJ/mol
dH reaction is -1173 + 1046 =-127kJ/mol
Answer:
acids or bases can be tested
by chemical indicators
Answer:
63. 55 amu
Explanation:
Copper is known to exist in two different isotopes which are Cu-63 and Cu-65.
Cu-63 has an atomic mass of 62.93 amu and it has an abundance of 69.15%.
Similarly,
Cu-65 has an atomic mass of 64.93 amu and it has an abundance of 30.85%
Therefore, using the weighted average mass method, the atomic mass of copper is:
Atomic mass of copper = (0.6915*62.93) amu + (0.3085*64.93) amu = 43.52 amu + 20.03 amu = 63.55 amu
Thus, the atomic mass of copper (express in two decimal places) is 63.55 amu
Answer:
8.99×10^-7m
Explanation:
The wavelength can be calculated using the expression below
E=hcλ
Where E= energy= 2.21 x 10^-19 J.
C= speed of light= 3x10^8 m/s
h= planks constant= 6.626 × 10^-34 m2 kg / s
E=hcλ
λ= E/(hc)
Substitute for the values
λ=( 2.21 x 10^-19 )/(6.626 × 10^-34 × 3x10^8 )
= 8.99×10^-7m
