Q.Choose the correct option.
The size of colloidal particles lies between-
a. 10⁻¹⁰ m and 10⁻⁹ m
b. 10⁻⁹ m and 10⁻⁶ m
c. 10⁻⁶ m and 10⁻⁴ m
d. 10⁻⁵ m and 10⁻² m
Step 1. Recall the size ranges given in the chapter. True solutions have solute particle diameters of about 0.1 to 2 nm; colloidal dispersions have dispersed-phase particle diameters of about 2 to 500 nm; suspensions have still larger particles, visible or nearly visible to the naked eye.
Step 2. Convert nanometres to metres. 2 nm = 2 x 10⁻⁹ m and 500 nm = 5 x 10⁻⁷ m, so the colloidal range in metres is roughly 10⁻⁹ m to 10⁻⁶ m (500 nm rounds up to the same order of magnitude as 10⁻⁶ m = 1000 nm).
Step 3. Match to the options. (a) 10⁻¹⁰-10⁻⁹ m is too small -- that is closer to individual atomic/ionic dimensions. (c) 10⁻⁶-10⁻⁴ m and (d) 10⁻⁵-10⁻² m are both too large -- those are suspension or visible-particle scales.
(b) 10⁻⁹ m and 10⁻⁶ m
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