Molarity and Molality

Question

Help please?

What is the molarity of a solution of 145 g NaCl in an aqueous solution with a total volume of 2.75 L?

How many grams of KCl are needed to prepare .750 L of a 1.50 M aqueous solution?

What is the molality of a solution of 75.2 g AgClO4 dissolved in 885 g C6H6?

What is the molality of 16.1 g of Cl2 dissolved in a 5000 g water?

What is the mole fraction of carbon monoxide (CO) in a mixture of 45.6 g CO and 899 g CO2

A gas mixture contains the following gases with mole fractions indicated in parentheses: methane (0.510), ethane (0.431), propane (0.011), butane (0.013) and acetylane (?). What is the mole fractionof acetylene

What is the molality of a solution prepared by dissolving 35 g NaCl in 250 g water?

What is the molality of a solution of 30 g KCl dissolved in 100 kg water?

What is the mole fraction of 18 mol NaCl in a solution of 100 mol water?

What is the mole fraction of 50 g Cl2 dissolved in a 100,000 liter pool? (Hint: 1 liter of water can be approximated as 1 kg of water)

Could someone please explain to me how to do these?

Really appreciated!

Answer 1

1.  
molecular mass for NaCl = 58.5 g/mol
number of mole of NaCl = 145 g / (58.5 g/mol)
                       =  2.479 mol
Molarity of NaCl = 2.479 mol x 2.75 L
                  = 0.901 M

Answer 2

A gas mixture contains the following gases with mole fractions indicated in parentheses: methane (0.510), ethane (0.431), propane (0.011), butane (0.013) and acetylane (?). What is the mole fraction of acetylene?

i need help answering this guestion ^_^
i would really appriciate it.