<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;
(3) Substance A is an element and substance Z is a compound.
Explanation;
-A compound is a substance formed when two or more chemical elements are chemically bonded together, such as water, carbon dioxide, methane, etc while an element is a pure chemical substance made of same type of atoms, such includes, oxygen, potassium, hydrogen, carbon, etc.
- Compounds can be broken
down or decomposed into simpler substances: elements cannot be broken down chemically into simpler substances .
False, in an exothermic reaction, an increase in temperature does not favor the formation of products. Instead, it favors the backward reaction. An exothermic reaction is a reaction where energy is transferred from the system out to the environment.
Solubility and temperatures are directly related. The higher the temperature of the solvent, the higher the solubility of the solute in the solvent.
Dissolving a solute in a solvent is an endothermic process hence providing heat favors the process. Higher temperatures cause the molecules of the solvent to have high kinetic energy hence bombard each other and with that of the solute with high frequency. This then ensures fast diffusion of the solute particles in the solvent.
<u>Moseley</u> discovered that <u>elements</u> with similar properties occurred at <u>regular intervals</u> when the elements were arranged in order of increasing
<u>"</u><u> </u><u>Atomic number </u><u>"</u>