<u>Hydrogen bonds </u>are weak bonds that are not strong enough to hold atoms together to form molecules but are strong enough to form bonds within and around large molecules.
- The hydrogen bond is weak bond.
- The hydrogen bond is electrostatic force of attraction between hydrogen atom and more electronegative atoms or group ( like Florine , oxygen or nitrogen) which is contently bonded.
- The hydrogen bond is occur in polar , contently bond atoms in different molecules.
- Example is H-O-H or

- The positively charged hydrogen side of one water molecule is bond with negatively charged oxygen side of another molecule.
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Answer:
The final and initial concentration of the acid and it's conjugate base are approximately equal, that is we use the weak acid approximation.
Explanation:
The Henderson-Hasselbalch is used to calculate the pH of a buffer solution. It depends on the weak acid approximation.
Since the weak acid ionizes only to a small extent, then we can say that [HA] ≈ [HA]i
Where [HA] = final concentration of the acid and [HA]i = initial concentration of the acid.
It also follows that [A^-] ≈ [A^-]i where [A^-] and[A^-]i refer to final and initial concentrations of the conjugate base hence the answer above.
Answer and Explanation:
The basic unit which are that are important in chemistry are meter, kilogram ,mol,
Candela which is the unit of luminous of intensity is not so important in physics
(a) SI unit of length is meter (m)
(b) Si unit of volume is 
(c) Si unit of mass is kilogram (kg)
(d) SI unit of time is second (s)
(e) SI unit of temperature is kelvin (K)
Boyle Law says “the pressure of fixed amount of ideal gas which is at constant temperature is
inversely proportional to its volume".<span>
P = 1/V
<span>Where, P is pressure of the ideal gas and V is volume of the ideal gas.</span>
<span>For two situations, this law can be added as;
P</span>₁V₁ = P₂V₂<span>
</span><span>14 lb/in² x V₁ = 70 lb/in² x 500 mL</span><span>
</span><span>V₁ =
2500 mL</span><span>
Hence, the needed volume of atmospheric air = 2500
mL
<span>Here, we made two </span>assumptions. They are,
1. The
atmospheric air acts as ideal gas.
2.
Temperature is a constant.
<span>We didn't convert the units to SI units since
converting volume and pressure are products of two numbers, they will cut off. </span></span></span>