Answer:
2.04 x 10²⁴ molecules
Explanation:
Given parameters:
Mass of Be(OH)₂ = 145.5g
To calculate the number of molecules in this mass of Be(OH)₂ we follow the following steps:
>> Calculate the number of moles first using the formula below:
Number of moles = mass/molarmass
Since we have been given the mass, let us derive the molar mass of Be(OH)₂
Atomic mass of Be = 9g
O = 16g
H = 1g
Molar Mass = 9 + 2(16 + 1)
= 9 + 34
= 43g/mol
Number of moles = 145.5/43 = 3.38mol
>>> We know that a mole is the amount of substance that contains Avogadro’s number of particles. The particles can be atoms, molecules, particles etc. Therefore we use the expression below to determine the number of molecules in 3.38mol of Be(OH)₂:
Number of
molecules= number of moles x 6.02 x 10²³
Number of molecules= 3.38 x 6.02 x 10²³
= 20.37 x 10²³ molecules
= 2.04 x 10²⁴ molecules
This noble gas is argon (Ar), because its third energy level is full.
Answer:
D. Visible Light
Explanation:
D is the right answer because visible light is perceived by humans as color and the rest aren't visible at all. For example, if you broke a bone and have to have an X-ray done, you can't see the x-rays. When you are heating something in the microwave, you can't see the waves. And when you are listening to the radio in the car, you also can't see the waves.
H2O
This equation is a double displacement reaction, and it forms H2CO3, which is very unstable and separates into H2O and CO2.
