Answer:
It means the chemical entity is a radical
Explanation:
When we talk of unsaturation, we are referring to the number of pi-bonds in a chemical entity. The alkane, alkene and alkyne organic family are used to as common examples to explain the term unsaturation.
While alkynes have 3 bonds, it must be understood that they have 2 pi bonds only and as such their degree of saturation is two.
In the case of an alkene, there is only one single pi bond and as such the degree of unsaturation is 1.
Now in this case, we have a fractional 0.5 degree of unsaturation alongside the 3 to make a total of 3.5. So what’s the issue here?
The fractional part shows that the chemical entity we are dealing with here is a radical. While the integer 3 shows that there are 3 pi-bonds, the half pi bond remaining tells us that there is a missing electron on one of the atoms involved in the chemical bonding and as such, the 1/2 extra degree of unsaturation tends to tell us this.
Kindly recall that a radical is a chemical entity within which we have at the least an unpaired electron.
Answer:
Single replacement reaction
Explanation:
Option B: high pressure and low temperature
A gas is more soluble under high pressure and low temperature conditions.
On increasing temperature of a gas, its kinetic energy increases. The increase in kinetic energy increases the motion of particles of gas this causes most of the gaseous particles to escape from the gas phase. Thus, less particles are available to dissolve in liquid and solubility decreases.
The effect of pressure on solubility of gas can be explained with the help of Henry's law. According to the law, at constant temperature, solubility of gas and partial pressure of gas are related to each other as follows:

Here, p is the partial pressure of the gas,
is Henry's law constant, and
c is the concentrate of the gas.
According to above relation, concentration of gas decreases on decreasing partial pressure. Thus, on increasing pressure, concentration of gas increases this increases the solubility of gas in liquid.
Therefore, solubility of gas is greatest at high pressure and low temperature.
Which sentence from "Black Hole Beginnings" contains a cause-and-effect relationship?
More matter mounts up on the outside, increasing the pressure on the inside.
Instead it is a dramatic melding, or blending, of atoms, called nuclear fusion.
Each atom has its own tiny center, or nucleus.
Surrounding each nucleus is an electrical force field..
Methanoic acid has a molecular formula of HCOOH, when form an ester it's HCOO-, so the rest of the ester is -C4H9, a saturated 4 carbon chain. As shown in the attached diagram, there are 4 structural isomers, and the third isomer has 2 stereoisomers. So the answers is D:5.