Answer:
- <u>C₂H₄</u> (option number 4)
Explanation:
A hydrocarbon with a <em>double bond</em> in its carbon skeleton is an alkene and has the general form:
- .
This is, the number of hydrogen atoms is twice the number of carbon atoms.
On the other hand, alkanes have only single bonds, and the compounds with a triple bond in its carbon skeleton are alkynes.
Review each choice:
1) <u>C₃H₈:</u>
- In this case, the number of hydrogen atoms is 2×3 + 2 = 6 + 2 = 8, which is corresponds to an alkane, not an alkene.
2)<u> C₂H₆</u>
- For this, the number of hydrogen atoms is 2 × 2 + 2 = 4 + 2 = 6. Again an alkane, not alkene.
3) <u>CH₄</u>
- Hydrogen atoms: 1 × 2 + 2 = 4 ⇒ an alkane
4) <u>C₂H₄ </u>
- Hydrogen atoms: 2 × 2 = 4. This is precisely the relation for an alkene, so this is the hydrocarbon that has a double bond in its carbon skeleton.
- The chemical formula may be writen as CH₂ = CH₂, to show the double bond.
So, this is the correct answer.
5) <u>C₂H₂</u>
- Hydrogen atoms: 2 × 2 - 2 = 4 - 2 = 2. This relation of carbon and hydrogen atoms corresponds to a compound with triple bond, i.e an alkyne: CH≡CH.
Answer:
semipermeability
Explanation:
partially but not freely or wholly permeable specifically : permeable to some usually small molecules but not to other usually larger particles a semipermeable membrane.
Answer: A.mol/kg
The SI (international system) unit for molality is mol / kg, or solute moles per kg of peptides. A solution with a molality of 1 mol / kg is often described as "1 molal" or "1 m".
Answer: The correct option is C ( is very hard and burns cleanly).
Explanation:
COAL is a form of rock that is made up of mostly carbon amongst other elements which includes sulphur, nitrogen, hydrogen and oxygen. There are different types of coal which include:
--> anthracite ( 90% carbon)
--> bituminous coal ( 70-90% carbon)
--> lignite ( 60- 70% carbon) and
--> peat (60 % carbon).
Anthracite is the type of coal that contains the highest carbon content ( 90% carbon). This makes it very hard and is often a times referred to as HARD COAL. Anthracite is a higher quality coal for domestic and open fire heating. This is because it contains less impurities than other type of coal and thereby making it to BURN CLEANLY avoiding atmospheric pollution.