Explanation:
entropy, the measure of a system's thermal energy per unit temperature that is unavailable for doing useful work. Because work is obtained from ordered molecular motion, the amount of entropy is also a measure of the molecular disorder, or randomness, of a system.
A metallic bond is a force that holds atoms together in a metallic substance.
4 is correct for this one
A precipitate is a product of a reaction that is insoluble in the reaction medium (usually water).
Why?
One of the signs that a reaction happened is that a precipitate forms. Let's take the reaction between Silver Nitrate (AgNO₃) and Sodium Chloride (NaCl) as an example:
AgNO₃(aq) + NaCl(aq) → AgCl(s)↓ + NaNO₃(aq)
In this reaction, Silver Chloride (AgCl) is an insoluble product of the reaction, and precipitates out of the reaction medium
If we write down the ionic equation, we find out the following:
Ag⁺ + NO₃⁻ + Na⁺ + Cl⁻ → AgCl(s) + Na⁺ + NO₃⁻
The ions that appear at both sides of the arrow are called spectator ions, since they are not directly involved in the process of the reaction, making the net ionic equation to be:
Ag⁺ + NO₃⁻ → AgCl(s)
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