Answer:
Precautions
Explanation:(Grammar Check)
The answer is 2 pairs. The carbon atom has 4 electrons and oxygen atom has 6 electrons. The purpose of shared electron is to get 8 electrons at the outer layer. So the carbon atom needs to share 4 electrons which is 2 pairs with oxygen to be stable.
Atomic mass Si = 28.0855 u.m.a
28.0855 g -------------------- 6.02x10²³ atoms
3.96x10³ g ------------------- ?? atoms
( 3.96x10³) x 6.02x10²³ / 28.0855 =
8.48x10²⁵ atoms
Answer : The molality of NaCl is, 1.95 mol/kg
Explanation :
Formula used for Elevation in boiling point :
where,
= change in boiling point = 
= boiling point constant for water = 
m = molality
i = Van't Hoff factor = 2 (for electrolyte)
The dissociation 
will be,
So, Van't Hoff factor = Number of solute particles = 
= 1 + 1 = 2
Now put all the given values in the above formula, we get:
Therefore, the molality of NaCl is, 1.95 mol/kg
Answer:
Cu₃(PO₄)₂(s), RbNO₃(aq)
Explanation:
This reaction looks like a possible <em>double replacement reaction</em>, in which the metal ions have exchanged partners.
3Cu(NO₃)₂(aq) + 2Rb₃PO₄(aq) ⟶ Cu₃(PO₄)₂ + 6RbNO₃
You must recall the pertinent <em>solubility rules</em>:
1. Salts of Group 1 elements (e.g., Rb⁺) are soluble.
2. Salts containing nitrate ions (NO₃⁻) are soluble.
3. Most salts containing phosphate ions (PO₄³⁻) are insoluble
According to Rules 1 and 1, RbNO₃ is soluble.
According to Rule 3, Cu₃(PO₄)₂ is insoluble.
∴ 3Cu(NO₃)₂(aq) + 2Rb₃PO₄(aq) ⟶ Cu₃(PO₄)₂(s) + 6RbNO₃(aq)
