Answer:
0.08 mL
Explanation:
The solution of the skin test has a concentration of 0.2% (w/v), which means that there are 0.2 g of the antigen per 100 mL of the solution. If a new solution will be done using it, then this solution will be diluted, and the mass of the antigen added must be the same in the volume taken and at the diluted solution.
The mass is the concentration (in g/mL) multiplied by the volume of the solution (in mL), so, if m is the mass, C the concentration, V the volume, 1 the initial solution, and 2 the diluted:
m1 = m2
C1*V1 = C2*V2
Where
C1 = 0.2 g/100 mL = 0.002 g/mL
V1 = ?
C2 = 0.04 mg/mL = 0.00004 g/mL
V2 = 4 mL
0.002*V1 = 0.00004*4
V1 = 0.08 mL
Mix it. The salt will dissolve, eventually the sand and metal will settle. Pour out most of the water, let it evaporate leaving the salt. Use a magnet for the iron, which leaves the sand.
Answer:
A star begins its life as a cloud of dust and gas (mainly hydrogen) known as a nebula. A protostar is formed when gravity causes the dust and gas of a nebula to clump together in a process called accretion. ... If a critical temperature in the core of a protostar is reached, then nuclear fusion begins and a star is born.
Explanation:
.
<u>Answer:</u> The number of atoms in spherical gold nano particle are 
<u>Explanation:</u>
- To calculate the volume of sphere, we use the equation:
where,
r = radius of the sphere = 
(Conversion factor: 
)
Putting values in above equation, we get:
- To calculate mass of of the substance, we use the equation:
Volume of gold = 
Density of gold = 
Putting values in above equation, we get:
- To calculate the number of moles, we use the equation:
Mass of gold = 
Molar mass of gold = 196.97 g/mol
Putting values in above equation, we get:
- According to mole concept:
1 mole of an element contains 
number of atom
So, 
moles of gold will contain = 
number of atoms.
Hence, the number of atoms in spherical gold nano particle are
