Answer:
There are approximately 1.54 moles in a 275 g sample of 
.
Explanation:
To find out number of moles, fistly we have to calculate molecular mass of .
There are 2 atoms of Potassium 1 atom of Chromium and 3 atoms of oxygen in the given compound.
For molecular mass we have to add the value of mass of 2 atoms of Potassium with mass of 1 atom of Chromium and with mass of 3 atoms of oxygen.
Atomic mass of Potassium = 39
Atomic mass of Chromium = 52
Atomic mass of Oxygen = 16
Now,
Molecular mass of = 
The molecular mass of a compound is the mass of compound in one mole.
To find out the number of moles, we have to divide given mass of compound by its molecular mass.
Hence the number of moles in 275 gm of is 1.54.
This uses the concept of freezing point depression. When faced with this issue, we use the following equation:
ΔT = i·Kf·m
which translates in english to:
Change in freezing point = vant hoff factor * molal freezing point depression constant * molality of solution
Because the freezing point depression is a colligative property, it does not depend on the identity of the molecules, just the number of them.
Now, we know that molality will be constant, and Kf will be constant, so our only unknown is "i", or the van't hoff factor.
The van't hoff factor is the number of atoms that dissociate from each individual molecule. The higher the van't hoff factor, the more depressed the freezing point will be.
NaCl will dissociate into Na+ and Cl-, so it has i = 2
CaCl2 will dissociate into Ca2+ and 2 Cl-, so it has i = 3
AlBr3 will dissociate into Al3+ and 3 Br-, so it has i = 4
Therefore, AlBr3 will lower the freezing point of water the most.
Explanation:
Electromagnetic wave Wavelength
(1) Microwave = 1 m to 1 mm = 
to 
(2) Ultraviolet = 10 nm to 400 nm
(3) Radio waves = 1 mm to 100 km = to 
(4) Infrared = 700 nm to 1 mm
(5) X-ray = 0.01 nm to 10 nm
(6) Visible = 400 nm t0 700 nm
a) In order of increasing wavelength:
: 5 < 2 < 6 < 4 < 1 < 3
b) Frequency of the electromagnetic wave given as:
= frequency
= Wavelength
c = speed of light
So, the increasing order of frequency:
: 3 < 1 < 4 < 6 < 2 < 5
c) Energy(E) of the electromagnetic wave is given by Planck's equation :
So, the increasing order of energy:
: 3 < 1 < 4 < 6 < 2 < 5
Answer:
Element symbol Cu
Number of protons 29
Number of electrons 28
Explanation:
To get the element symbol, we need the name of the element. To correctly identify the name of the element, we need the proton number.
Now the mass number is 65 and the number of neutrons is 36. The number of protons is this the mass number minus the number of neutrons. This equals 65 - 36 = 29 protons.
The element with 29 protons is copper Cu.
Now to get the number of electrons, for an electrically neutral atom , the number of electrons equals the number of protons. But here, the atom is not electrically neutral anymore as it has now formed a univalent positive ion of +1.
To form a positive ion, you have to do so by losing electrons. The atom in question here has just lost one electron. Thus, our of the 29, it is left with only 28 electrons.
