A system is a part of the <em>physical</em> universe defined <em>arbitrarily</em> for observation purposes.
Boundaries are a part of the <em>physical</em> universe that are around the system.
In a scientific sense, a system is a part of the <em>physical</em> universe whose boundaries, that is, the limit between the system and its surroundings, are defined <em>arbitrarily</em> for observation purposes.
A system contains at least a model, represented in a phenomenological way, and it can be isolated (no mass nor energy interactions), closed (no mass interactions) or open.
The surroundings are a part of the <em>physical</em> universe that are around the system.
An example is a coffee-maker, where coffee-maker the system and air represents the surroundings, the coffee-maker receives energy from a heat source to warm up itself and releases part of such energy to the air.
We kindly invite to check this question on systems and surroundings: brainly.com/question/6044762
The swimming pools pH is below 7, meaning it is slightly acidic. If you want to make the pH higher, you must add a base which by definition has a pH higher than 7.
D. Add base
Rubidium would exhibit the greatest shielding [ effect. ]
Answer:
0.7457 g is the mass of the helium gas.
Explanation:
Given:
Pressure = 3.04 atm
Temperature = 25.0 °C
The conversion of T( °C) to T(K) is shown below:
T(K) = T( °C) + 273.15
So,
T₁ = (25.0 + 273.15) K = 298.15 K
Volume = 1.50 L
Using ideal gas equation as:

where,
P is the pressure
V is the volume
n is the number of moles
T is the temperature
R is Gas constant having value = 0.0821 L.atm/K.mol
Applying the equation as:
3.04 atm × 1.50 L = n × 0.0821 L.atm/K.mol × 298.15 K
<u>⇒n = 0.1863 moles</u>
Molar mass of helium = 4.0026 g/mol
The formula for the calculation of moles is shown below:
Thus,

<u>0.7457 g is the mass of the helium gas. </u>