Quick help with chemistry with molarity

Determine the molarity of a solution made by dissolving 2 moles of sugar in 10 L of water.
Answer
1. 20M
2. 0.2M
3. 1.5M
4. 3M


How many moles of lithium are in 5 g of lithium?
Answer
1. 15 moles
2. 1.67 moles
3. 0.71 moles
4. 35 moles


To determine the number of water molecules in 10 g of water, one would
Answer
1. divide by the molar mass, then multiply by Avogadro's number
2. multiply by the molar mass, then multiply by Avogadro's number
3. multiply by the molar mass, then divide by Avogadro's number
4. divide by the molar mass, then divide by Avogadro's number

1. M = mol/L

2 mol/10 L = 0.2 M


Answer: 0.2 M


2. Given g x (1 mol/molar mass) = mol Li

Molar (atomic) mass Li: 6.94 g/mol


5 g Li x (1 mol Li/6.94 g Li) = 0.720


Answer: 0.71 moles


3. 10 g x (1 mol/molar mass) x (6.022x10^23 molecules/1 mol)

Answer: 1. divide by the molar mass, then multiply by Avogadro's number

Determine the molarity of a solution made by dissolving 2 moles of sugar in 10 L of water.
Answer

Molarity = 2 moles sugar / 10 L water = 0.2 mols/L.

How many moles of lithium are in 5 g of lithium?
Answer

1 mol lithium = 6.941 grams. 5 / 6.941 = 0.7203 mols lithium.

2. 0.2 M (Molarity = moles/ volume in litres)

3. 0.71 moles ( moles = mass in grams / molar mass )

#watermolecules = moles of water * avogadro's #
and to find moles of water you need to divide mass by molar mass
so answer is #1

Molarity is mol/L therefore 2mol/10L= 2M

lithium has the atomic mass 6.941 g/mol therefore 5g/6.941=0.71mol

g * mol/g * A/mol = number of molecules (1.)