Answer:
Freezing and boiling point
Explanation:
A liquid form of any substance is an intermediate form between the solid form and the gaseous form.
Decreasing the temperature of liquid water according to the phase diagram of 
would freeze it and we would have a phase change from liquid to solid (ice) at the freezing point of water.
Similarly, heating water to its boiling point would evaporate water and we would have a phase change from liquid to gas (water vapor).
Therefore, liquid water exists between its freezing and boiling point.
Answer: This option is incorrect: <span>B. Covalent compounds are held together by much stronger interparticle forces than are ionic compounds.
Justification:
Ionic bonds, held by ionic compounds, are much stronger than covalent bonds, held by covalent compounds.
In ionic bonds one element yields one or more electrons forming a cation (a positively charged ion) and the other element accepts the electrons forming an anion (a negatively charged ion).
The anion and the cation are electrostatically atracted by each other. This electrostatic atraction force, named ionic bond, is very strong.
As result of this, the ionic compounds form strong crystals with high boiling and fusion points. A good example of this the sodium chloride, formed by the union of cation Na(+) and anion Cl(-).
The covalent bonds are result of sharing electrons and do not form ions. This bond is weaker than the ionic bond.
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Answer:
4.083 * 10^20 atoms.
Explanation:
One Mole of phosphorus contains 6.022 * 10^23 atoms (Avogadros number)'
Since 1 mole of Phosphorus has a mass of 30.974 grams, 21 milligrams has
6.022 * 10^23 * 0.021 / 30.974
= 0.004083 * 10^23
= 4.083 * 10^20
Answer: 1.Sulfuric acid is a catalyst
2. Vanadium(v) oxide is a catalyst
