<span>The student should
follow following steps to make 1 L of </span>2.0 M CaCl₂.<span>
<span>
1. First he should
calculate the number of moles of 2.0 M CaCl</span></span>₂ in 1 L solution.<span>
</span>Molarity of the solution = 2.0 M<span>
Volume of solution which should be prepared = 1 L
Molarity =
number of moles / volume of the solution
Hence, number of moles in 1 L = 2 mol
2. Find
out the mass of dry CaCl</span>₂ in 2 moles.<span>
moles =
mass / molar mass
Moles of CaCl₂ =
2 mol</span><span>
Molar mass of CaCl₂ = </span><span>110.98 g/mol
Hence, mass of CaCl</span>₂ = 2 mol x <span>110.98 g/mol
= 221.96
g
3. Weigh the mass
accurately
4. Then take a cleaned and dry1 L volumetric flask and place a funnel top of it. Then carefully add the salt into the volumetric flask and
finally wash the funnel and watch glass
with de-ionized water. That water also should be added into the volumetric
flask.
5. Then add some
de-ionized water into
the volumetric flask and swirl well until all salt are
dissolved.
<span>6. Then top up to
mark of the volumetric flask carefully.
</span></span>
7. As the final step prepared solution should be labelled.
Answer:
According to avogadro's law, 1 mole of every substance contains avogadro's number 
of particles and weighs equal to its molecular mass.
To calculate the moles, we use the equation:
a. moles in 14.08 g of 
= 
molecules in 14.08 g of = 
b. moles in 17.75 g of NaCl = 
molecules in 17.75 g of 
= 
formula units 17.75 g of =
c. moles in 20.06 g of 
= 
formula units in 20.06 g of = 
The subscriot 2 means that in the formula there are two parts of K, and the subscript 1 (implicit) for S, indicates that there is one part of S.
This is, the formula gives the ratio of the elements K and S in the compound, which is:
2 atoms of K : 1 atom of S.
Answer: there are 2 atoms of K and 1 atom of S in a molecule of K2S.
Answer:
An orbital is a region in space where there is a high probability of finding an electron.
Explanation:
The orbital is a concept that developed in quantum mechanics. Recall that Neils Bohr postulated that the electron occupied stationary states which he called energy levels. Electrons emit radiation when the move from a higher to a lower energy level. Similarly, energy is absorbed by an electron to move from a lower to a higher orbit.
This idea was upturned by the Heisenberg uncertainty principle. This principle state that the momentum and position of a particle can not be simultaneously measured with precision.
Instead of defining a 'fixed position' for the electron, we define a region in space where there is a possibility of finding an electron with a certain amount of energy. This orbital is identified by a set of quantum numbers.
