Is air a compound mixture or a element. compound
Answer:
As a substance melts, and goes from a solid to a liquid state, the kinetic energy of the molecules increases, and the molecules move faster, and they separate further and further away from each other. The intermolecluar forces holding the molecules together become weaker. This is why a liquid can take fill the shape of its container, whereas a solid has a fixed shape.
Explanation:
take your notes man
Answer: There are 7.4 moles of helium gas present in a 1.85 liter container at the same temperature and pressure.
Explanation:
Given: 
= 2.25 L, 
= 9.0 mol
= 1.85 L, 
= ?
Formula used to calculate the moles of helium are as follows.
Substitute the values into above formula as follows.
Thus, we can conclude that there are 7.4 moles of helium gas present in a 1.85 liter container at the same temperature and pressure.
Answer:
669.48 kJ
Explanation:
According to the question, we are required to determine the heat change involved.
We know that, heat change is given by the formula;
Heat change = Mass × change in temperature × Specific heat
In this case;
Change in temperature = Final temp - initial temp
= 99.7°C - 20°C
= 79.7° C
Mass of water is 2000 g ( 2000 mL × 1 g/mL)
Specific heat of water is 4.2 J/g°C
Therefore;
Heat change = 2000 g × 79.7 °C × 4.2 J/g°C
= 669,480 joules
But, 1 kJ = 1000 J
Therefore, heat change is 669.48 kJ
