Answer:
a)The total number of platinum atoms are
.
b)The radius of a Pt atom is 138.7 pm.
Explanation:
a) Let the total number of platinum atoms be x
And mass of x atoms of platinum be m
Edge length of platinum cube ,s= 1.0 cm
Volume of the cube = 
Density of the platinum cube = 
Mass = Density × Volume

Mass of an atom of platinum = 


b) If only 74 percent of the space inside the cube is taken up by Pt atoms.
Volume occupied by platinum atoms = 74% of 

Volume occupied by
atoms is
.



The radius of a Pt atom is 138.7 pm.
N: 106Answer:
72 protons, 106 neutrons, 72 electrons.
Explanation:
to solve this use this simple method: APEMAN.
A= atomic number, P= Protons, E= Electrons.
M= Mass, A= atomic number, N= neutrons.
1. APE (atomic number, protons, electrons) are the same. since Hf (Hafnium) atomic number is 72, Hf has 72 protonsand ele ctrons.
2. to get Neutrons it will be mass-atomic number= neutrons.(M-A=N)
Hf mass= 178. So, 178-72= 106 neutrons.
Answer:
it doesnt even give you enough information for you to answer it
Explanation:
Answer:
1. Percentage by weight = 0.5023 = 50.23 %
2. molar fraction =0.153
Explanation:
We know that
Molar mass of HClO4 = 100.46 g/mol
So the mass of 5 Moles= 5 x 100.46
Mass (m)= 5 x 100.46 = 502.3 g
Lets assume that aqueous solution of HClO4 and the density of solution is equal to density of water.
Given that concentration HClO4 is 5 M it means that it have 5 moles of HClO4 in 1000 ml.
We know that
Mass = density x volume
Mass of 1000 ml solution = 1 x 1000 =1000 ( density = 1 gm/ml)
m'=1000 g
1.
Percentage by weight = 502.3 /1000
Percentage by weight = 0.5023 = 50.23 %
2.
We know that
molar mass of water = 18 g/mol
mass of water in 1000 ml = 1000 - 502.3 g=497.9 g
So moles of water = 497.7 /18 mole
moles of water = 27.65 moles
So molar fraction = 5/(5+27.65)
molar fraction =0.153
So,
Recall Newton's Second Law of Motion: force = mass x acceleration
Also recall:
acceleration = velocity/time
velocity = distance/time
Distance is expressed in meters.
Time is expressed in seconds.
Mass is expressed in kilograms.
v = m/s
a = m/s^2
F = m * a
F = kg * m/s^2

The unit for force is the Newton (N).