200mL of 0.001 M solution NaOH is combined with 300 mL of a 0.002 M solution of HCL. How many moles of H ions?

Question

( In the final solution)

Answer 1

First write the balanced equation

NaOH + HCl....> NaCl + H2O

Mole ratio: 1 : 1 ...> 1:1

Considering the coefficients before each of the reactant and product in balanced chemical equation, we can say 1 mole of NaOH reacts with one mole of HCl, to yeild one mole of NaCl and one mole of water.

Keeping that in mind....

Now let's work out the amount of moles we got here.

NaOH: 0.001M solution means there are 0.001 moles in 1000 ml. So we can calculate how many moles would be in 200ml = 0.001/5 =0.0002 moles.

HCl; 0.002M solution means there are 0.002 moles in 1000ml. So the # of moles in 300 ml= (0.002 X 300)/1000 = 0.0006 moles

We have only 0.0002 moles of NaOH and only 0.0002 moles of HCl would react with that. (Since the eqaution suggest that they react in one to one mole ratio). 0. 0004 moles of HCl would remain unreacted.

This HCl ionize in the system
HCl.....> H+(aq) + Cl-(aq)
ratio: 1....> 1: 1

One mole of HCl would ionize to provide one mole of H+ ions and one mole of Cl- ions. Since we got 0.0004 moles of HCl, the # of moles of H+ ion produced would be 0.0004 moles.

Got it?

Answer 2

200mL of 0.001M NaOH has 0.2mmol OH ion.
300mL of 0.002M HCl has 0.6mmol H ion.

The reaction between H and OH ions occur on a 1:1 ratio, producing neutral water. Since H is in excess, all the OH will be used up in the reaction. Subtracting 0.2 from 0.6 gives 0.4mmol of excess H ion in the final solution.

Answer 3

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