The mass of piece of sterling silver jewelry is 33.24 g. It contains 92.5% silver Ag by mass. Since, sterling silver is an alloy of Ag-Cu thus, percentage of Cu will be:
% Cu=100-92.5=7.5%
Thus, mass of copper will be:
Molar mass of Cu is 63.546 g/mol, thus, number of moles of Cu can be calculated as follows:
Here, m is mass and M is molar mass.
Putting the values,
Now, in 1 mole of Cu there are thus, in 0.03923 mol, number of Cu atoms will be:
Thus, number of atoms of Cu will be.
The wavelength of light : 4.14 x 10⁻⁵ m
<h3>Further explanation </h3>Radiation energy is absorbed by photons
The energy in one photon can be formulated as
Where
h = Planck's constant (6,626.10⁻³⁴ Js)
f = Frequency of electromagnetic waves
The energy of the light = 4.8 x 10⁻²¹ J
The wavelength of light :
Answer: 54.4 kJ/mol
Explanation:
First we have to calculate the moles of HCl and NaOH.
The balanced chemical reaction will be,
From the balanced reaction we conclude that,
As, 1 mole of HCl neutralizes by 1 mole of NaOH
So, 0.05 mole of HCl neutralizes by 0.05 mole of NaOH
Thus, the number of neutralized moles = 0.05 mole
Now we have to calculate the mass of water:
As we know that the density of water is 1 g/ml. So, the mass of water will be:
The volume of water =
Now we have to calculate the heat absorbed during the reaction.
where,
q = heat absorbed = ?
= specific heat of water =
m = mass of water = 100 g
= final temperature of water =
= initial temperature of metal =
Now put all the given values in the above formula, we get:
Thus, the heat released during the neutralization = 2.72 KJ
Now we have to calculate the enthalpy of neutralization per mole of :
0.05 moles of releases heat = 2.72 KJ
1 mole of releases heat =
Thus the enthalpy change for the reaction in kJ per mol of HCl is 54.4 kJ