Why does the grass be green
D = m / V
It even gives you the density of gold in the problem. Major hint. Once you know the volume (using V = m / D) then you can calculate the height (thickness) from the equation...
V = L x W x H
Volume = Length x Width x Height
start by converting 200.0 mg into grams
1000 mg = 1 g
200. mg x (1 g / 10^3 mg) = 0.200 g
V = m / D
V = 0.200 g / (19.32 g/cm^3)
V = 0.01035 cm^3
Convert 2.4 ft and 1 ft to cm
2.4 ft x (12 in / 1 ft) x (2.54 cm / 1 in) = 73.15 cm
1 ft = 30.48 cm
Compute the height (thickness)
V = LxWxH
H = V / LW = 0.01035 cm^3 / 73.15 cm / 30.48 cm
H = 4.64 x 10^-6 cm
Convert to nanometers
4.64 x 10^-6 cm x (1 m / 100 cm) x (10^9 nm / 1 m) = 46.4 nm
Knowing the atomic radius of gold, I might have asked my students for the minimum number of gold atoms in this thickness of gold. This would assume that the gold atoms are all in a row. This would give the minimum number of gold atoms.
Atomic radius gold = 174 pm
Diameter = 348 pm
46.4 nm x (1 m / 10^9 nm) x (10^12 pm / 1 m) x (1 Au atom / 248 pm) = 133 atoms of gold
Explanation:
- Let lactic acid be represent as HA. And, pH is given as 2.75.
Hence, concentration of hydrogen ions will be calculated as follows.
pH =
= M
= 0.00178 M
The reaction equation will be as follows.
Initial: 0.025 0 0
Change: -0.00178 0.00178 0.00178
Equilibrium: 0.0232 0.00178 0.00178
Hence, calculate the value of as follows.
=
=
Therefore, value of the equilibrium constant is
.
- Another method that we can use to determine the value of of any weak acid is when weak acid is titrating with a strong base then,
number of moles of acid = moles of salt formed by (acid + base)
These moles of salt are actually known as half equivalence point. So, at this point we need we need to measure the pH of solution with the help of a device called pH meter.
As we known that pH =
and,