Answer : The correct option is C.
Explanation :
Chemical change : It is defined as a change in which a new compounds are formed by the chemical reaction. Changes occurs in their chemical composition and properties.
The molecular structure of a substance changes in a chemical reaction is a chemical change.
- Change in molecular structure means that there is a breaking and formation of bonds in a molecule.
The example of chemical change in terms of change in molecular structure is the reaction of hydrogen with oxygen.
The reaction of hydrogen with oxygen is,

In this reaction, the H-H bond is break and O-H bond is form.
Answer:
12.8 g of
must be withdrawn from tank
Explanation:
Let's assume
gas inside tank behaves ideally.
According to ideal gas equation- 
where P is pressure of
, V is volume of
, n is number of moles of
, R is gas constant and T is temperature in kelvin scale.
We can also write, 
Here V, T and R are constants.
So,
ratio will also be constant before and after removal of
from tank
Hence, 
Here,
and 
So, 
So, moles of
must be withdrawn = (0.66 - 0.26) mol = 0.40 mol
Molar mass of
= 32 g/mol
So, mass of
must be withdrawn = 
Answer:
Polar
Explanation:
A polar climate is a place where the climate usually has a temperature below freezing, icy, and covered in snow. These areas do not get direct heat and sunlight from the sun. Polar climates are located at the North Pole of the Arctic, and at the South Pole on the continent of Antarctica.
It is approximately 10 ^ -10
Answer: 72 grams of
are needed to completely burn 19.7 g 
Explanation:
According to avogadro's law, 1 mole of every substance weighs equal to molecular mass and contains avogadro's number
of particles.
To calculate the number of moles, we use the equation:

Putting in the values we get:


According to stoichiometry:
1 mole of
requires 5 moles of oxygen
0.45 moles of
require=
moles of oxygen
Mass of 
72 grams of
are needed to completely burn 19.7 g 