To measure the density of the stone placed in a graduated cylinder let us follow these steps bellow
- Measure the volume of water poured into a graduated cylinder
- Place the object in the water and remeasure the volume.
- The difference between the two volume measurements is the volume of the object.
- Divide the mass by the volume to calculate the density of the object.
<em>We know that the formula for density is given as </em>
Given data
Mass = 8gram
Initial Volume of water in cylinder = 25mL
Final Volume of water in cylinder = 29mL
Hence the volume of the rock = 29-25 = 4mL
Therefore the density of the rock = 8/4 = 2 g/mL
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Potassium oxide: K₂O.
There's no need for prefixes since K₂O is an ionic compound.
<h3>Explanation</h3>
Find the two elements on a periodic table:
- Potassium- K- on the left end of period four.
- Oxygen- O- near the right end of periodic two.
Elements on the bottom-left corner of the periodic table are metals. Those on the top-right corner are nonmetals.
- Potassium is a metal,
- Oxygen is a nonmetal.
A metal and a nonmetal combine to form an ionic compound. Potassium oxide is likely to be an ionic compound. It contains two types of ions:
- Potassium ions: Potassium is group 1 of the periodic table. It is an alkaline metal. Like other alkaline metals such as sodium Na, potassium K tends to lose one electron and form ions of charge +1 in compounds. The ion would be K⁺.
- Oxide ions from oxygen: Oxygen is the second most electronegative element on the periodic table. It tends to gain two electrons and form the oxide ion
when it combines with metals.
The two types of ions carry opposite charges. They shall pair up at a certain ratio such that they balance the charge on each other. The charge on each ion is twice that on a 
ion. Each would pair up with two . Hence the subscript in the formula: 
.
There are two classes of compounds:
- Covalent compounds, which need prefixes, and
- Ionic compounds, which need no prefix.
Prefixes are needed only in covalent compounds. For instance in the covalent compound carbon dioxide 
, the prefix di- indicates that there are two oxygen atoms in the formula . However, there's no need for prefix in ionic compounds such as 
.
So we look equation for the free Gibbs free energy (ΔG) which depends on entalpy (ΔH), temperature (T) and entropy (ΔS):
ΔG = ΔH - TΔS
ΔG is negative (-) because the water absorption on the silica gel surface is a spontaneous process.
ΔH is negative (-) because the water absorption on the silica gel surface is a exothermic process (it releases heat and if you want to desorb the water form the silica gen you need to add heat which is a endothermic process).
ΔS is negative (-) because the water is adsorbed, so from disorderly state you take the water molecules and put them in a orderly state and by doing that you decrease the entropy.
CO2 goes on the bottom and O2 on the top.
