Answer:
36.66%
Explanation:
Step 1: Given data
- Mass of the sample: 2.875 g
Step 2: Calculate the mass of salt
The mass of the sample is equal to the sum of the masses of the components.
m(sample) = m(iron) + m(sand) + m(salt)
m(salt) = m(sample) - m(iron) - m(sand)
m(salt) = 2.875 g - 0.660 g - 1.161 g
m(salt) = 1.054 g
Step 3: Calculate the percent of salt in the sample
We will use the following expression.
%(salt) = m(salt) / m(sample) × 100%
%(salt) = 1.054 g / 2.875 g × 100% = 36.66%
Explanation:
Relation between entropy change and specific heat is as follows.
The given data is as follows.
mass = 500 g, 
= 24.4 J/mol K
= 500 K, 
= 250 K
Mass number of copper = 63.54 g /mol
Number of moles = 
= 
= 7.86 moles
Now, equating the entropy change for both the substances as follows.
![7.86 \times 24.4 \times [T_{f} - 250]](https://tex.z-dn.net/?f=7.86%20%5Ctimes%2024.4%20%5Ctimes%20%5BT_%7Bf%7D%20-%20250%5D)
= ![7.86 \times 24.4 \times [500 -T_{f}]](https://tex.z-dn.net/?f=7.86%20%5Ctimes%2024.4%20%5Ctimes%20%5B500%20-T_%7Bf%7D%5D)
= 750
So, 
= 
- For the metal block A, change in entropy is as follows.
= ![24.4 log [\frac{375}{500}]](https://tex.z-dn.net/?f=24.4%20log%20%5B%5Cfrac%7B375%7D%7B500%7D%5D)
= -3.04 J/ K mol
- For the block B, change in entropy is as follows.
= ![24.4 log [\frac{375}{250}]](https://tex.z-dn.net/?f=24.4%20log%20%5B%5Cfrac%7B375%7D%7B250%7D%5D)
= 4.296 J/Kmol
And, total entropy change will be as follows.
= 4.296 + (-3.04)
= 1.256 J/Kmol
Thus, we can conclude that change in entropy of block A is -3.04 J/ K mol and change in entropy of block B is 4.296 J/Kmol.
The atomic mass of the isotope Ni ( 62 over 28 ) = 61.928345 amu.
Mass of the electrons: 28 · 5.4584 · 10^(-4 ) amu = 0.0152838 amu ( g/mol )
Mass of the nuclei:
61.928345 amu - 0.0152838 amu = 61.913062 amu (g/mol)
The mass difference between a nucleus and its constituent nucleons is called the mass defect.
For Ni ( 62 over 28 ): Mass of the protons: 28 · 1.00728 amu = 28.20384 amu
Mass of the neutrons: 34 · 1.00866 amu = 34.299444 amu
In total : 62.49828 amu
The mass defect = 62.49828 - 61.913062 = 0.585218 amu
Nucleus binding energy:
E = Δm · c² ( the Einstein relationship )
E = 0.585218 · ( 2.9979 · 10^8 m/s )² · 1 / (6.022 · 10^23) · 1 kg / 1000 g =
= 0.585218 · 8.9874044 · 10 ^16 : (6.022 · 10^23) · 0.001 =
= ( 5.2595908 : 6.022 ) · 0.001 · 10^(-7 ) =
= 0.0008733 · 10^(-7) J = 8.733 · 10^(-11) J
The nucleus binding energy per nucleon:
8.733 · 10^(-11) J : 62 = 0.14085 · 10 ^(-11) =
= 1.4085 · 10^(-12) J per nucleon.
<span>Moles = 0.252
Molarity = 1.07
This question is badly worded. You're asking for moles and I suspect you really want molarity. The number of moles of ammonium chloride you have in the solution will remain constant regardless of the volume of the solution. However, the molarity of the solution will differ depending upon how concentrated it is. So I'll give you both the number of moles of ammonium chloride you have, and the molarity of the resulting solution. Please talk to your teacher if you're confused by the difference between moles and molarity.
The formula for ammonium chloride is NH4Cl. So let's calculate it's molar mass. Start by looking up the associated atomic weights.
Atomic weight nitrogen = 14.0067
Atomic weight hydrogen = 1.00794
Atomic weight chlorine = 35.453
Molar mass NH4Cl = 14.0067 + 4 * 1.00794 + 35.453 = 53.49146 g/mol
Moles NH4Cl = 13.5 g / 53.49146 g/mol = 0.252376735 mol
Molarity is defined as moles per liter, so let's divide the number of moles we have by the volume in liters. So:
0.252376735 mol / 0.235 l = 1.073943551 M
Rounding to 3 significant figures gives: 0.252 moles, 1.07 molarity.</span>
