Molarity problem?

Question

please help in solving..

>How many milligrams of NaHCO3 are in a 500mg tablet if 40.00ml of 0.120M HCL is required to neutralize the sample?

>How many milliliters of 0.250M KOH will react with 15.0ml of 0.350M H2SO4?

*all the numbers in the chemical formulas are subscripts

THANKS!!! =D

Answer 1

NaHCO3 + HCl --> NaCl + H2O + CO2^

In this reaction, the result of completion is neutral only if all the CO2 is driven off.

It takes 1 mole of HCl to neutralize 1 mole of NaHCO3. 40ml of 0.12M HCl has 0.04*0.12 moles of HCl = 0.0048 moles. Therefore there were 0.0048 moles of NaHCO3. The molecular mass of that is 84g/mole, so 0.0048 moles is 0.4032g or 403.3mg

2KOH + H2SO4 --> 2H2O +K2SO4

2 moles of KOH for each mole of H2SO4 are needed

15ml of 0.350M H2SO4 is 0.35*0.015 moles 0.00525 moles; so the moles of KOH reacted is .0105 moles

0.0105 = V*0.250, V = 0.042L = 42mL

Formulas to remember:

Molarity times volume = moles
Molecular mass times moles = actual mass