Answer:
Melting of ice
Explanation:
A physical change is one in which just the physical properties of the matter is altered. Most phase changes reaction falls under this type of change.
- Examples are boiling, melting, freezing, condensation, sublimation, magnetization of metals, breaking glass, cutting wood.
- No new kinds of matter is formed.
- The process is reversible
- No change in mass
Answer: 0.25 mol
Explanation:
Use the formula n=N/NA
n= number of mols
N = number of particles
Nᵃ = Avogadros constant = 6.02 x
So, n=
The 10 to the power of 23 cancels out and you are left with 1.505/6.02, which is approximately 1/4. This is the same as 0.25 mol.
Hope this helped :)
Answer:
Percent yield = 84.5 %
Explanation:
Given data:
Mass of methanol = 229 g
Actual yield of water = 219 g
Percent yield of water = ?
Solution:
Chemical equation:
2CH₃OH + 3O₂ → 2CO₂ + 4H₂O
Number of moles of methanol:
Number of moles = mass/ molar mass
Number of moles = 229 g/ 32 g/mol
Number of moles = 7.2 mol
Now we will compare the moles of water with methanol.
CH₃OH : H₂O
2 : 4
7.2 : 4/2×7.2 = 14.4 mol
Mass of water:
Mass = number of moles × molae mass
Mass = 14.4 mol × 18 g/mol
Mass = 259.2 g
Percent yield:
Percent yield = actual yield / theoretical yield × 100
Percent yield = 219 g / 259.2 g × 100
Percent yield = 84.5 %
Explanation:
The more reactive element replaces less reactive element during chemical reaction.
Since, potassium is more reactive than beryllium. When potassium reacts with beryllium choride, it replaces beryllium and forms potassium chloride and produces beryllium.
Answer:-
Carbon
[He] 2s2 2p2
1s2 2s2 2p2.
potassium
[Ar] 4s1.
1s2 2s2 2p6 3s2 3p6 4s1
Explanation:-
For writing the short form of the electronic configuration we look for the nearest noble gas with atomic number less than the element in question. We subtract the atomic number of that noble gas from the atomic number of the element in question.
The extra electrons we then assign normally starting with using the row after the noble gas ends. We write the name of that noble gas in [brackets] and then write the electronic configuration.
For carbon with Z = 6 the nearest noble gas is Helium. It has the atomic number 2. Subtracting 6 – 2 we get 4 electrons. Helium lies in 1st row. Starting with 2, we get 2s2 2p2.
So the short term electronic configuration is [He] 2s2 2p2
Similarly, for potassium with Z = 19 the nearest noble gas is Argon. It has the atomic number 18. Subtracting 19-18 we get 1 electron. Argon lies in 3rd row. Starting with 4, we get 4s1.
So the short electronic configuration is
[Ar] 4s1.
For long term electronic configuration we must write the electronic configuration of the noble gas as well.
So for Carbon it is 1s2 2s2 2p2.
For potassium it is 1s2 2s2 2p6 3s2 3p6 4s1
