Multiply,
moles * molar mass = mass
Answer:
The periodic table of elements puts all the known elements into groups with similar properties. This makes it an important tool for chemists, nanotechnologists, and other scientists. If you get to understand the periodic table and learn to use it, you'll be able to predict how chemicals will behave.
T<span>his is a straightforward question related to the surface energy of the droplet. </span>
<span>You know the surface area of a sphere is 4π r² and its volume is (4/3) π r³. </span>
<span>With a diameter of 1.4 mm you have an original droplet with a radius of 0.7 mm so the surface area is roughly 6.16 mm² (0.00000616 m²) and the volume is roughly 1.438 mm³. </span>
<span>The total surface energy of the original droplet is 0.00000616 * 72 ~ 0.00044 mJ </span>
<span>The five smaller droplets need to have the same volume as the original. Therefore </span>
<span>5 V = 1.438 mm³ so the volume of one of the smaller spheres is 1.438/5 = 0.287 mm³. </span>
<span>Since this smaller volume still has the volume (4/3) π r³ then r = cube_root(0.287/(4/3) π) = cube_root(4.39) = 0.4 mm. </span>
<span>Each of the smaller droplets has a surface area of 4π r² = 2 mm² or 0.0000002 m². </span>
<span>The surface energy of the 5 smaller droplets is then 5 * 0.000002 * 72.0 = 0.00072 mJ </span>
<span>From this radius the surface energy of all smaller droplets is 0.00072 and the difference in energy is 0.00072- 0.00044 mJ = 0.00028 mJ. </span>
<span>Therefore you need roughly 0.00028 mJ or 0.28 µJ of energy to change a spherical droplet of water of diameter 1.4 mm into 5 identical smaller droplets. </span>
Answer:
Approximately 
.
Explanation:
Lookup Avogadro's Number: 
(three significant figures.)
Lookup the relative atomic mass of 
, 
, and 
on a modern periodic table:
(For example, the relative atomic mass of is 
means that the mass of one mole of 
atoms would be approximately 
grams on average.)
The question counted the number of 
molecules without using any unit. Avogadro's Number 
helps convert the unit of that count to moles.
Each mole of molecules includes exactly 
of these 
molecules.
molecules would correspond to 
of such molecules.
(Keep more significant figures than required during intermediary steps.)
The formula mass of gives the mass of each mole of 
molecules. The value of the formula mass could be calculated using the relative atomic mass of each element:
.
Calculate the mass of approximately 
of :
.
(Rounded to three significant figures.)
.
.