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3 subatomic particles- protons, electrons and neutrons

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Did you notice that?

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Average mass has unit of amu @ u. While Ar and Mr are dimensionless.
How to convert average mass (with unit) to Ar/Mr (without unit)?

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Nucleon number= Atomic mass = Mass number
Formula to find average mass of C?
Remember Qimi/Qi !

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Cth soalan:
Given molality of NaOH solution is 2.5m. If the density of solution is 1.5g/mL, calculate molarity of the solution.

Tips: Assume mass of solvent 1 kg.

*you may assume from density but some students get stuck

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Can you distinguish them?

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Example:
How many liters of 0.350 M NaOH solution can be prepared from 400.0 mL of 3.60 M solution?

Answer:
M₁V1 = M₂V₂

(3.6M)(400mL) = (0.35M)V₂
V₂ = 4,110 mL
= 4.11 L

How much water added?
VH2O = (4110-400)mL
= 3710 mL