4) the ice has to be heated up to above 0c first, as it is continuing to cool the water back toward 0c
5) 0.0338 kcal
(33.8/1000)
6) 1.2506 kcal
((33.8*37.0)/1000)
Answer:
a) Explain why:
(i) All the elements of a group have similar chemical properties.
(ii) All the elements of a period have different chemical properties.
(b) The atomic radii of three elements X, Y and Z of a period of the periodic table are 186 pm, 104 pm and 143 pm respectively. Giving a reason arrange these elements in the increasing order of atomic number in the period.
Answer:
Group 14
Explanation:
The elements of the Periodic Table are arranged into 18 Groups.
Among the "main group elements" — those in Groups 1, 2 and 13 to 18 — the number of valence electrons — the number of electrons in the outermost energy level — corresponds to the last digit of the Group number.
Thus, Group 14 contains the elements with four valence electrons — C, Si, Ge, Sn, Pb, and Fl.
1) You neeed to know and use the Ksp for BaF2.
At 25°C this Ksp is 1.0 * 10 ^ - 6
2) The solutibility of BaF2 is given by:
BaF2 ⇄ Ba(2+) + 2F(-)
x 2x
=> Ksp = x * (2x)^2 = 4x^3
3) When you have a NaF solution, you have to take into accout the concentration of the NaF solution
M = 0.1
Now the equilibrium species are:
BaF2 ⇄ Ba(2+) + 2F(-)
x 2x + 0.10
And Ksp = x* [2x + 0.10]^2 = 1.0 * 10 ^ -6
Given that the Ksp << 1 you may assume that 2x << 0.1 => 2x + 0.1 ≈ 0.1
=> 1.0 * 10 ^ - 6 ≈ x(0.1)^2 = 0.01x
=> x = 1.0 * 10^ -6 / 0.01 = 1.0 * 10^ - 4 M = 0.0001 M
That is the molar solubility.
4) Now, you calculate the number of moles from the molarity's formula:
M = n / v => n = M * v = 0.0001 M * 0.500 l = 0.00005 mol
And now convert to grams,
mass in grams = number of moles * molar mass
molar mass of BaF2 = 175.34 g/mol
mass in grams = 0.00005 moles * 175.34 g / mol = 0.0088 g
Answer: 0.0088 g
A definition of "matter" more fine-scale than the atoms and molecules definition is: matter is made up of what atoms and molecules are made of, meaning anything made of positively charged protons, neutral neutrons, and negatively charged electrons. There are three states of matter, they are: solid, liquid and gas. In extreme environments, other states may be present, such as plasma, Bose-Einstein condensates and neutron stars .