How would you..?

Question

Question 1
How would you separate:
1- a mixture of powdered copper sulfate and powdered copper metal?
2- a solid alloy (amalgam) of gold and mercury)
3- a mixture of sugar, iron filings and aluminium powder?

Question 2:
If a metal Y forms a phosphate compound with the formula YPO4, what would be the correct formual for the sulfide of Y?
a) YS
b) YSO4
c) Y2S
d) Y2(SO4)3
e) Y2S3

Question 3:
If you are given the atomic number of an element, which of the following would you already know?
a) mass number
b) number of possble isotopes
c) number of neutrons
d) number of electrons in the nucleus of the atom
e) number of electrons in a neutral atom of the element

Question 4:
Which of the following correctly defines the mass number of a given atom?
a) the total number of neutrons, protons and electrons in the atom

b) the total number of neutrons and protons in the nucleus of the atom

c) the number of neutrons in the nucleus of the atom

d) the total mass of neutrons, protons and electrons in the atom

e) the total mass of neutrons and protons in the nucleus of the atom

Answer 1

Question 1 -- How would you separate:
1- a mixture of powdered copper sulfate and powdered copper metal?

Disolve the Copper sulfate in hot water and filter to remove the Copper metal. Evaporate the filtrate to get the Copper sulfate back.

2- a solid alloy (amalgam) of gold and mercury)

The best solution is to use a suitable retort to distill the mercury out of the amalgam. You could also dissolve the mercury in Nitric acid and filter this solution to separate the Gold. Getting back the Mercury metal would require a little additional work because you would need to reduce the Mercury nitrate salt.

3- a mixture of sugar, iron filings and aluminium powder?

Use a magnetic field to remove the Iron. Then dissolve the sugar in hot water and filter. The Aluminum will be in the filter. The sugar could be recovered by evaporation of the filtrate.

Question 2 -- If a metal Y forms a phosphate compound with the formula YPO4, what would be the correct formual for the sulfide of Y?

e) Y2S3 -- The phosphate anion has a -3 charge, but the Sulfide is only -2

Question 3 -- If you are given the atomic number of an element, which of the following would you already know?

e) number of electrons in a neutral atom of the element
This must be equal to the number of protons (which is the same as the atomic number)

If you were highly trained as a specalist in nuclear and atomic physics, then you MIGHT also know
b) number of possble isotopes
but more likely, you would have to look this up.

Question 4 -- Which of the following correctly defines the mass number of a given atom?

b) the total number of neutrons and protons in the nucleus of the atom

Answer 2

1. Copper sulfate is soluable in water while powdered copper metal is not.
2. React the amalgam with a strong acid. Gold will not react while mercury will.
3. Get the iron filings out with a magnet. Put the rest of the mixture in water. Sugar will dissolve while the aluminum powder will not. So you can filter the solution. The sugar solution will pass through the filter while the aluminum powder will not.

Q2. the Y ion will have a 3+ charge since PO4 has a 3- charge. Therefore, since sulfur usually has a -2 charge in the sulfide, the correct formula would be E (Y2S3)

Q3. Atomic number is the number of protons in an element. It has nothing to do with a, b, or c. For D, electrons are never in the nucleus of an atom. E. is correct. For a neutral atom, there are exactly the same number of protons and electrons.