<h2>Answer:</h2>
Compound. Option A is correct
<h2>Explanations:</h2>
When two or more different elements combines, a compound is formed. For instance, if carbon and oxygen combines, carbondioxide is formed according to the equation;
From the reaction, carbon and oxygen are the elements while carbondioxide is the compound. Hence we can conclude that a pure substance formed when two or more different elements combine called compound.
The answer is one dot.
The number of dots an element has represented in the diagram, indicates how many valence eletrons( which is the number of electrons in the most exterior energy level of an atom or ion) the element has. So, 1 valence eletron equals one dot.
Answer:
0.508 mole
Explanation:
NOTE: Since no hydrogen is attached to the compound given in question above, it means the compound is CCl₄.
The number of mole present in 78.2 g of CCl₄ can be obtained as follow:
Mass of CCl₄ = 78.2 g
Molar mass of CCl₄ = 12 + (35.5×4)
= 12 + 142
= 154 g/mol
Mole of CCl₄ =?
Mole = mass / molar mass
Mole of CCl₄ = 78.2 / 154
Mole of CCl₄ = 0.508 mole
Therefore, 0.508 mole is present in 78.2 g of CCl₄
To determine what gas is this, we use Graham's Law of Effusion where it relates the rates of effusion of gases and their molar masses. We do as follows:
r1/r2 = √(M2 / M1)
Let 1 be the the unkown gas and 2 the H2 gas.
r1/r2 = 0.225
M2 = 2.02 g/mol
0.225 = √(2.02 / M1)
M1 = 39.90 g/mol
From the periodic table of elements, most likely, the gas is argon.
