You find an unknown substance that cannot be separated by filtration, evaporation,

It's not enough.

Explanation:

To be able to separate mixtures into substances we have more methods than just distillation, filtration and evaporation. Certain mixtures cannot be filtered, however by decanting can be separated simpler substances from it. Centrifugation separates solids dispersed in liquids that cannot be separated by filtration. Also, it is necessary to try to separate the substance by the method of chromatography, crystallization, etc.

Have a nice day!

Explanation:

If unknown capacitance C1, C2, C3 and C4 are connected in series to one another, their equivalent capacitance of the circuit will be expressed as shown

Given the capacitance's 3.0 pF, 2.0 pF, 5.0 pF and X pF connected in series to each other. If the equivalent capacitance of the circuit is 0.83 pF, then to get X, we will apply the formula above;

C₄ ≈ 6pF

Hence the value of the X capacitor is approximately 6pF