Answer:
127529 KJ
Explanation:
Since 1gallon = 3.78 L= 3780 ml
The density of C8H18= 0.703 g/mL
Density = mass/volume
Mass= Density × volume
Mass= 0.703 g/mL × 3780 ml
Mass= 2657.34 g
Molar mass of C8H18= 114 g/mol
Number of moles= mass/molar mass
Number of moles= 2657.34/114
Number of moles= 23.31 moles
Since 1 mole evolved=5471 kJ
23.31 moles = 5471 kJ × 23.31 = 127529 KJ
The Molarity of a solution = number of moles / volume.
Volume = 244ml = 0.244L
So it follows that number of moles = Molarity * volume
Number of moles = 0.135 * 0.244 = 0.03945.
Hence the number of moles = 0.03945
Answer:
78.3 × 10²³ atoms of helium are present in 52 g.
Explanation:
Given data:
Mass of He = 52 g
Number of atoms = ?
Solution:
First of all we will calculate the number of moles of He
Number of moles = mass /molar mass
Number of moles = 52 g/ 4 g/mol
Number of moles = 13 mol
The given problem will solve by using Avogadro number.
It is the number of atoms , ions and molecules in one gram atom of element, one gram molecules of compound and one gram ions of a substance.
The number 6.022 × 10²³ is called Avogadro number.
For example,
1 mole = 6.022 × 10²³ atoms of helium
13 mol × 6.022 × 10²³ atoms of helium / 1 mole
78.3 × 10²³ atoms of helium
