<u>Answer:</u>
The correct answer option is 1.6 atm.
<u>Explanation:</u>
We know that there is a sample gas which has a volume of 2.4 L with a pressure 1.2 atm and we are to find the pressure of the same gas sample if its volume is reduced to 1.8 L at a constant temperature.
We will apply the Boyle's law here which states that the "pressure of a given mass of an ideal gas is inversely proportional to its volume at a constant temperature".
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Substituting the values in the formula to get:

Therefore, the pressure of the same gas sample will be 1.6 atm if the volume is reduced to 1.8 L at a constant temperature.
translate please I'm confused
Explanation:
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Answer: -
15.55 M
35.325 molal
Explanation: -
Let the volume of the solution be 1000 mL.
Density of nitric acid = 1.42 g/ mL
Total Mass of nitric acid Solution = Volume of nitric acid x Density of nitric acid
= 1000 mL x 1.42 g/ mL
= 1420 g.
Percentage of HNO₃ = 69%
Amount of HNO₃ = 
= 979.8 g
Molar mass of HNO₃ = 1 x 1 + 14 x 1 + 16 x 3 = 63 g /mol
Number of moles of HNO₃ = 
= 15.55 mol
Molarity is defined as number of moles per 1000 mL
We had taken 1000 mL as volume and found it to contain 15.55 moles.
Molarity of HNO₃ = 15.55 M
Mass of water = Total mass of nitric acid solution - mass of nitric acid
= 1420 - 979.8
= 440.2 g
So we see that 440.2 g of water contains 15.55 moles of HNO₃
Molality is defined as number of moles of HNO₃ present per 1000 g of water.
Molality of HNO₃ = 
= 35.325 molal
<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.
learn about Hydrogen bond
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