Question

It is written as 3.0 M HCl. What does the “M” mean for “3.0 M HCl”?

In the reaction, bubbles form which indicates that the reaction is going. What are those bubbles of gas made of?

What is the purpose of heating up the reaction mixture?

Why would not add too much HCl to the reaction mixture?

the reaction is washing soda (Na2CO3) and 3M HCl

Answer 1

Given reaction:

PART 1:

3 M HCl means 3 molar (M) HCl.

Molar (M) is the unit of molarity (concentration) = mol/L = no.of moles of solute in 1 L of solution.

PART 2:

From the above reaction, we can see that the products except CO₂ are in soluble form.

But CO₂ is in gaseous state, and tends to escape out of the solution.

These, CO₂ gaseous molecules can be seen in the form of bubbles escaping out of the liquid.

PART 3:

NaCl is a soluble salt.

If NaCl is produced in larger amount during reaction, the solution will reach a saturation point and no more NaCl can be dissolved.

At this point, the rate of reaction tends to slow down, since the solution doesn't want NaCl anymore.

Hence, if temperature is increased, the solubility of NaCl salt in solution will increase, and thereby the reaction will continue with a higher rate.

PART 4:

We need both reactants in same amount to do a reaction. If a reactant is less in amount, and consumed completely in a reaction, then it is called a limiting reagent.

When HCl is added in excess, Na₂CO₃ will become a limiting reagent and will be completely consumed during the reaction.

Hence, after a while, the solution becomes acidic due to higher amount of HCl.