Help please! I can't solve any of these, would someone be as kind as to show me the answers?

Question

How many moles of NaHCO3 are in a 125.0 g sample of the compound?

3. How many moles are in 6.73 x 1024 water molecules?

4-5. AgBr, a chemical used in photography can be made with this reaction:

2AgNO3 + CaBr2 „³ 2AgBr + CaN2O6

4. AgNO3 is very expensive, so in making AgBr, you want to be sure this reactant is all used up. If a chemist starts with 15.0 g of AgNO3, how many grams of CaBr2 must be added to use up all of the AgNO3?

5. How many moles of CaN2O6 are produced when 46.8 g or AgNO3 react?

6. DDT, an insecticide banned in the US, has the formula C14H9Cl5? Find its percent composition.

Answer 1

How many moles of NaHCO3 are in a 125.0 g sample of the compound?
moles = grams/molar mass

3. How many moles are in 6.73 x 1024 water molecules?
1 mole of anything contains 6.02 x 10^23 anythngs; therefore, 1 mole of water molecules will contain 6.02 x 10^23 molecules of water. So convert t moles by .....

4-5. AgBr, a chemical used in photography can be made with this reaction:
I don't know what you've had in class to answer this question but AgBr can be made in a number of different ways. One way is
NaBr + AgNO3 ==> AgBr + NaNO3.

Answer 2

Number 4 answer is 8.81