Answer:
B. 0.5 molar
Explanation:
Given data:
Initial concentration = 0.40 M
Initial volume = 750 mL
Final volume =750 - 150 mL = 600 mL
Final concentration = ?
Solution:
Molarity is the number of moles of solutes in litter of solvent. In given problem it is stated that when the solution is uncovered solvent evaporate it means molarity is changed. we can calculate the new molarity with the following formula.
C₁V₁ = C₂V₂
C₁ = initial concentration
V₁ = initial volume
C₂ = final concentration
V₂ = final volume
Now we will put the values in formula.
C₁V₁ = C₂V₂
0.40 M × 750 mL = C₂ × 600 mL
300 M.mL / 600 mL = C₂
0.5 M = C₂
Answer:
45.77 × 10²³ atoms
Explanation:
Given data:
Number of moles of iron = 7.6 mol
Number of atoms = ?
Solution:
Avogadro number:
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.
1 mole = 6.022 × 10²³ atoms
7.6 mol × 6.022 × 10²³ atoms / 1 mol
45.77 × 10²³ atoms
Answer:
1. Ice at 0 degrees C.
2. N₂ at STP.
3. N₂ at STP.
4. Water vapor at 150 degrees C and 1 atm.
Explanation:
First, we need to remember that entropy (S) is a <em>measure of how spread out or dispersed the energy of a system is among the different possible ways that system can contain energy</em>. The greater the dispersal, the greater is the entropy.
When the temperature is increased, the energies associated with all types of molecular motion increase. Consequently, the entropy of a system always increases with increasing temperature.
With this in mind, we consider the pairs:
1. Since the ice at 0ºC has a greater temperature than the ice at -40 ºC, the first has the higher entropy.
2. The N₂ at STP (that is, 1 atm and 25 ºC) has higher entropy than N₂ at 0ºC and 10 atm because it has a higher temperature and less pressure, which allows a greater dispersal of energy by the molecules of the gas.
3. The N₂ at STP has a higher entropy since it has a higher temperature than N₂ at 0ºC, even though it the first has a lower volume (24,4 L vs. 50 L).
4. The water vapor at 150 ºC and 1 atm have a higher temperature and a lower pressure. This means that its molecules will have an increased molecular motion than the molecules of water vapor at a lower temperature and higher pressure. Therefore, the first has the highest entropy.
Adding energy to a matter causes a physical change. Head to water becomes vapor--taking energy away also causes physical change, (water becoming ice,) when heat is the energy being removed.
