Answer:
0.4383 g
Explanation:
Molality is defined as the moles of the solute present in 1 kg of the solvent.
It is represented by 'm'.
Thus,
Given that:
Mass of solvent, water = 150 g = 0.15 kg ( 1 g = 0.001 g )
Molality = 0.050 m
So,
Molar mass of NaCl = 58.44 g/mol
Mass = Moles*Molar mass = 
= 0.4383 g
Exothermic.
To remember this, ‘exo’ means outside, and ‘thermic’ means heat. It gives the outside (exo), heat (thermic).
Answer:
10.10
Explanation:
Step 1: Write the basic dissociation reaction for pyridine
C₅H₅N(aq) + H₂O(l) ⇌ C₅H₅NH⁺(aq) + OH⁻(aq) Kb = 1.9 × 10⁻⁹
Step 2: Calculate [OH⁻]
For a weak base, we will use the following expression.
[OH⁻] = √(Cb × Kb) = √(9.2 × 1.9 × 10⁻⁹) = 1.3 × 10⁻⁴ M
Step 3: Calculate pOH
We will use the definition of pOH.
pOH = -log [OH⁻] = -log 1.3 × 10⁻⁴ = 3.9
Step 4: Calculate pH
We will use the following expression.
pH = 14 - pOH = 14 - 3.9 = 10.10
