A chemical change affects on the molecular level of matter, which makes it irreversible. Combustion is a pretty good exmple. Physical changes are reversible and dont alter the formula. Hope this helped!
Answer:
trans-1,3-pentadiene is more stable than 1,4-pentadiene due to presence of a conjugated double bond.
Explanation:
Here, 
H(hydrogenated pdt.) is same for both 1,4-pentadiene and 1,3-pentadiene as they both produce pentane after hydrogenation
H(diene) depends on stability of diene.
More stable a diene, lesser will be it's H(diene) value (more neagtive).
trans-1,3-pentadiene is more stable than 1,4-pentadiene due to presence of a conjugated double bond.
Hence, 
is higher (less negative) for trans-1,3-pentadiene
Answer:
Explanation:
N and P will have similarity
Electronic configuration of N
2,5
1s²2s²p⁵
Electronic configuration of P
1s²2s²2p⁶3s²3p⁵
Electronic configuration bears similarity.
Both have 5 electrons in their outermost orbits . So they exhibit similarity in their properties. Both belong to the same 15 th group of periodic table.
Sr and Rb too bear much similarity . Both are strongly electro-positive metal , difference in their atomic no being only one.
Answer:
c.boron-11
Explanation:
The atomic mass of boron is 10.81 u.
And 10.81 u is a lot closer to 11u than it is to 10u, so there must be more of boron-11.
To convince you fully, we can also do a simple calculation to find the exact proportion of boron-11 using the following formula:
(10u)(x)+(11u)(1−x)100%=10.81u
Where u is the unit for atomic mass and x is the proportion of boron-10 out of the total boron abundance which is 100%.
Solving for x we get:
11u−ux=10.81u
0.19u=ux
x=0.19
1−x=0.81
And thus the abundance of boron-11 is roughly 81%.
Answer:
an estimate of the strength of a bond.
Explanation:
The bond order is given as;
1/2(number of bonding electrons - number of anti bonding electrons)
The bond order tells us about the strength of bond. As the bond order increases, so does the strength of the bond because atoms involved in bonding come closer to each other as the bond length decreases.
Hence, bond order is an index of bond strength. Triple bonds are stronger than double bonds which are stronger than single bonds.
