Answer:
D. They have the same number of valence electrons
Explanation:
- The periodic table arranges elements into rows known as periods and columns known as groups or families.
- Elements in the same group share similar chemical properties.
- Additionally, they have the same number of valence electrons. For example, elements in group I have one valence electrons while those in group II have two valence electrons.
- Elements in the same period share similar features such as having the same number of energy levels. For example elements in period 4 have four energy levels.
Answer: A closed system, because energy can enter or leave the container, but the water molecules cannot
Explanation:
Open system: In this system energy and matter both have access to their surroundings beyond the boundaries of system. .
Closed system :In this type system only energy has an access to its surroundings beyond the boundaries of system but not matter.
Isolated system:In this type system exchange of both energy and matter are restricted to move outside the boundaries of system.
According to question, the system given is a closed system because energy is transferred from the burner to glass flask and from the glass flask to the water (matter). But water molecules are only getting condensed on the inside surface of the flask that is exchange of matter beyond the boundaries of the system is restricted. Hence, closed system ,A closed system, because energy can enter or leave the container, but the water molecules cannot.
The answer is 69.048%.
Mass of potassium dichromate (K₂Cr₂O₇) is 294 g, which is a 100%.
Given mass of chromium is 52 g. So, the mass percent of chromium in the compound is 17.687%:
52 g : x% = 294 g : 100%
x = 52 ÷ 294 × 100 %
x = 17.687%
Given mass of potassium is 39 g. <span>So, the mass percent of potassium in the compound is 13.265%:
39 g : x% = 294 g : 100%
x = </span>39 ÷ <span>294 × 100 %
x = 13.265%
Therefore, </span>the mass percent of oxygen in the compound is <span>69.048%:
100% - </span>17.687% - <span>13.265% = 69.048%.</span>
Star clusters is the only thing i can think of that would apply.
