urgent calculation help please exam tomorrow please

[Habib]

Hi everyone

Can someone be kind enough to help me out with these questions ( Please see attachments).
Help is needed urgently, I have already asked around but have not got any answers.
Any help or guidance would be appreciated! Thanks

Question 1: Fluoride is added to tap water at a rate of 0.7ppm. How many milligrams of fluoride are present in two litres of such water?
Question 2: What is the molarity of a 0.7 ppm solution of fluoride?
Question3: if 50cm3 of a 5mMolar solution is diluted to one litre. What is the concentration of the resultant solution?
Answer for this is 2.5mM and i used C1V1=C2V2
Question 4: how many milligrams of glucose (C6H12O6) would need to be dissolved in 100cm3 water to give a 1mM solution?
Question 5: 50 cm3 of a 2mM solution of Sodium hydroxide is mixed with 50 cm3 of a 1mM solution of potassium hydroxide. What is the concentration of hydroxide ions in the resulting solution?

[Nik]

For starters -

1) 1 ppm is 1g in 1,000,000 ml. So 0.7ppm is 0.7g in 1,000,000 ml. Work out for 2 litres.

2) Molarity typically measured in moles/litre. So work out how many g in 1L, then use formula no of moles = mass/relative atomic mass

3) Are you sure this is right ?

4) Similar to q2. Work out relative molecular mass of glucose first.