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.
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Answer:
Percentage yield = 85.2%
Explanation:
Given data:
Mass of Mg = 21.3 g
Actual yield of MgO = 30.2 g
Percentage yield = ?
Solution:
Chemical equation:
2Mg + O₂ → 2MgO
Number of moles of Mg = mass/molar mass
Number of moles of Mg = 21.3 g / 24.3 g/mol
Number of moles of Mg = 0.88 mol
Now we will compare the moles of MgO with Mg.
Mg : MgO
2 : 2
0.88 : 0.88
Mass of MgO:
Mass of MgO= moles × molar mass
Mass of MgO= 0.88 mol × 40.3g/mol
Mass of MgO = 35.46 g
Actual yield of MgO = 30.2 g
Percentage yield:
Percentage yield = Actual yield/theoretical yield × 100
Percentage yield = 30.2 g/ 35.46 g × 100
Percentage yield = 85.2%
Answer:
Number of moles = 0.042 mol
Explanation:
Given data:
Number of moles = ?
Mass of calcium carbonate = ?
Solution:
Formula:
Number of moles = mass/ molar mass
now we will calculate the molar mass of calcium carbonate.
atomic mass of Ca = 40 amu
atomic mass of C = 12 amu
atomic mass of O = 16 amu
CaCO₃ = 40 + 12+ 3×16
CaCO₃ = 40 + 12+48
CaCO₃ = 100 g/mol
Now we will calculate the number of moles.
Number of moles = 4.15 g / 100 g/mol
Number of moles = 0.042 mol
Answer:
The answer is D. gamma rays
Explanation:
A radioactive atom can have three different types of emission:
alpha particles (α) = they have a mass of 4 amu and they have a very low penetrating power.
Beta particles (β) = they have 5x
amu and they have an intermediate penetrating power
Gamma rays (γ) = they are not particles basically just energy so its mass is ≈ 0 and its penetrating power is higher
For this reason Gamma emissions (γ) has the smallest mass value.