Answer:
1) Dissolve the crude substance in a minimum amount of hot solvent.
2) Filter the hot solution to remove the solid impurities (if present)
3) Allow the solution to cool slowly so crystals form.
4) Filter the crystals.
5) Dry the crystals
6) Weigh the crystals into a tared flask.
Explanation:
Recrystallization is a method used in chemistry to obtain crystals having a high degree of purity for the purpose of analytical or synthetic laboratory work.
Answer:
Ca:
Explanation:
A Lewis structure shows the number of valence electrons about an atom.
Ca is in Group 2 of Period 4.
Its electron configuration is [Ar]4s².
Thus, Ca has two valence electrons and its Lewis structure is Ca:
Answer: 17.34 grams of alum will be produced if 0.9875 g of Aluminium foil was used.
Explanation: Reaction to form alum from Aluminium is given as:
We are given Aluminium to be the limiting reactant, so the formation of alum will be dependent on Aluminium because it limits the formation of product.
By stoichiometry,
2 moles of Al is producing 2 moles of Alum
Mass of 2 moles of Aluminium = (2 × 27)g/mol = 54 g/mol
Mass of 2 moles of alum = (2 × 474)g/mol = 948 g/mol
54 g/mol of aluminium will produce 948 g/mol of alum, so
Amount of Alum produced = 17.34 grams
Theoretical yield of alum = 17.34 grams.
The number of protons and the number of neutrons determine an element's mass number: mass number
Answer:
XeF₂
Explanation:
Let's call the compound as XeaFb, where a and b are the number of atoms of each element. In the beginning, the partial pressure of XeaFb was 16 torr. By Dalton's Law, the total pressure of a gas mixture is the sum of the partial pressures of the components, so:
pH₂ = 64 - 16 = 48 torr
The reaction that happened was:
XeaFb + (b/2)H₂ → aXe + bHF
The stoichiometry of the reaction is 1:b/2:a:b. If all the XeaFb reacts:
1 torr of XeaFb -------- b/2 torr of H₂
16 torr -------- x
By a simple direct three rule:
x = 16b/2 = 8b torr of H₂ reacts
1 torr of XeaFb -------- a torr of Xe
16 torr -------- x
x = 16a torr of Xe is formed
Thus, 8b + 16a = 32
b + 2a = 4
The empirical formula is the minimum integer number of the elements in the compound. So, let's suppose a = 1 because fluorine can do only one bond, thus it's unprovable that will be more than one Xe bonded with one F:
b + 2*1 = 4
b = 2
Thus, the empirical formula is XeF₂.