Answer:
It matters
Explanation:
Pure substance are known to have a sharp freezing point. However, the presence of solute lowers the freezing point of the solvent. The best time to measure the freezing point is when the freezing process is just beginning.
It will be an error to measure the freezing point when the part of the solution has already frozen.
Answer:
- The option <u><em>B) Fe₂O₃ (s) + 3C(s) → 2Fe(s) + 3CO₂(g),</em></u> because the reactants are only solid units and the products contain gas molecules.
Explanation:
A <em>positive entropy change</em> means that the entropy of the products is greater than the entropy of the reactants.
Entropy in a measure of the radomness or disorder of the system.
Let's see every reaction:
<u />
<u>A) 4NO₂ (g) + 2 H₂O (l) + O₂ (g) → 4 HNO₃ (aq)</u>
Since 5 molecules of a gas (high disorder) combines with 2 molecules of liquid to produce 4 units of aqueous HNO₃ you may expect that the product is more ordered than the reactants, which means that the change in entropy is negative (the entropy decreases).
<u />
<u>B) Fe₂O₃ (s) + 3C(s) → 2Fe(s) + 3CO₂(g)</u>
The left side (reactants) show only solid substances which is a highly ordered arrangement while the right side (products) show the formation a solid (ordered arrangement) and a gas (highly disoredered arrangement), so you can predict the increase of the system entropy, i.e. a positive entropy change.
The <u>equation C)</u> shows the combination of 12 gas molecules to produce 1 solid and 6 gas molecules, so you can expect that the entropy will decrease, i.e. a negative entropy change.
For <u>equation D)</u> the products include solid and gas reactants while the product is just one unit of solid substance, letting you to predict a negative entropy change.
Compounds are not possible to be separated by physical means
Answer:
2 and 3 because there are the protons and neutrons which have a greater mass than the electrons which are found in the locations 1 and 4. The atom contains a nucleus, which is made from protons and neutrons, and electrons which are found around the nucleus. The mass of the atoms is concentrated in the very tiny space represented by the nucleus. Of course the electrons have a mass too, but is very small compared to the protons and neutrons, and we usually neglect its mass.
