### Higher - Avogadro Q

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• #### Message 1.

Posted by MissChemTeacher_Bitesize (U15172316) on Sunday, 3rd February 2013

Hey Guys!

Here are a few multiple choice Avogadro Questions to get you thinking.

The Avogadro Constant is the same as the number of:

A molecules in 16 g of oxygen
B ions in 1 litre of sodium chloride solution, concentration 1 mol l–1
C atoms in 24 g of carbon
D molecules in 2 g of hydrogen.

The mass of 1 mol of sodium is 23g.

What is the approximate mass of one sodium atom?

A 6 × 10²³g
B 6 × 10¯²³g
C 3.8 × 10¯²³g
D 3.8 × 10¯²⁴g

If you need any help with these questions get in touch

• #### Message 2

, in reply to message 1.

Posted by MissChemTeacher_Bitesize (U15172316) on Monday, 18th February 2013

Hey Guys!

Solutions to the Avogadro problems:

Q1)
A) 1 mole of O₂ (32g) = 6.02 x 10²³ molecules. We have 16g of oxygen molecules which is half a mole so it'll have half the number of molecules.

16g of O₂ = 0.5 x 6.02 x 10²³ = 3.01 x 10²³ molecules.

B) 1 mol/l of sodium chloride (Na⁺Cl¯) contains 1 mole and Avogadro's number of positive sodium ions and one mole (Avogadro's number) of negative chloride ions.

Total number of ions = 2 x 6.02 x 10²³ = 1.204 x 10²³ ions

C) 1 mole of Carbon (12g) = 6.02 x 10²³ atoms. We have 24g of carbon so it will have double the number of carbon atoms.

24g of C = 2 x 6.02 x 10²³ = 1.204 x 10²³ atoms

D) 1 mole of H₂ (2g) = 6.02 x 10²³ molecules.

The answer here is D

Q2) 1 mole of sodium (23g) contains Avogadro's constant number of sodium atoms, we need to calculate the mass of one sodium atom.

6.02 x 10²³ atoms ---------------> 1 mole of sodium (23g)
1 atom ------------------> 1 x 23 / 6.02 x 10²³ = 3.8 x 10¯²³g

The answer here would be D too.

If you need any help with the working of these answers get in touch.
Cheers Miss_Chem

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