Question

Hi everyone. I'm so confused with how to identify which is the limiting reagent and excess reagent from my lab of: Reacting sodium bicarbonate with hydrochloric acid, and then incubating it for 24 hours to get crystallization. Please help! Please D:

Answer 1

This is my lab's objective: To use a known mass of sodium bicarbonate, react it with hydrochloric acid and use a balanced chemical equation to predict, then verify, the mass of sodium chlorid produced. And here's my lab:

1. Make sure the electronic balance digital readout shows 0.00. If it shows any other value, press the "tare" button once.
2. Place the empty 150-mL beaker on the electronic balance. Allow the value to become steady, which will take about 3 seconds. Record this value in your data table. Then, press the tare button. The balance will reset to 0.000. If it is slightly off, wait 3 seconds, then press tare again.
3. Remove the beaker from the balance and add approximately 1/2 spoonful of sodium bicarbonate.
4. Return the beaker to the electronic balance and allow the value to become steady. Do not press tare. Record this value (the mass of sodium bicarbonate) on your data table.
5. Pour about 20 mL of hydrochloric acid into a 100-mL beaker. Place a medicine dropper in the beaker. DO NOT put the medicine dropper down anywhere but the beaker.
6. Add 3 drops of acid to the beaker containing the sodium bicarbonate, moving the dropper so that no drops land on each other. The idea is to spread out the adding of acid so as to hold all splatter within the beaker.
7. Continue to add acid slowly drop by drop. As liquid begins to build up, gently swirl the beaker. This is done to make sure unreacted acid reaches unreacted sodium bicarbonate. Do not add acid while swirling.
8. Your goal is to stop adding acid when all bubbling has ceased. In other words you want to add just enough hydrochloric acid to react with all of the sodium bicarbonate. When all bubbling has ceased, swirl the beaker and then add ONE last DROP of acid and swirl. If no bubbling happens, you are done. DO NOT add more acid then is absolutely necessary.
9. Take your beaker to incubator in the biology lab. Turn on the incubator and leave the beaker overnight.

Answer 2

The balanced chemical equation is:

\[NaHCO _{3} (s) + HCl (aq) -> NaCl (aq) + CO _{2} (g) + H _{2}O (l) \]

Answer 3

I ran a reaction of 4.56 g of sodium bicarbonate with 20 mL of hydrochloric acid

Answer 4

The beaker (150-mL): 77.47 g
beaker (150-mL) + NaHCO3 = 82.03 g
When incubated = 87. 43 g

Answer 5

I am so confused... please help D:

Answer 6

I also have to convert the hydrochloric acid's mL to grams. To convert HCL's mL to grams I have to find the molarity, multiply by the molarity (divided by 1000) to get moles and then divide by the molar mass of HCL? What's molarity?

Answer 7

Okay first thing, it seems according to your protocol that you don't have any limiting reagent for this reaction as you took a given number of moles of bicarbonate and reacted it with hydrochloric acid drop wise until there was no more noticeable reaction so in other words you used just enough acid for your whatever amount of base.

Answer 8

really? oh noo.. D:

Answer 9

Also we had 20 mL of HCl but it still wouldn't stop bubbling so one of my lab group member poured like 5 mL of HCl to cease the bubbles D:

Answer 10

er... so you used exactly 25mL of HCl?

Answer 11

Around, but we're only supposed to use 20 mL of HCl

Answer 12

If it is 20 mL of HCl, there's no limiting reagent?

Answer 13

Well, the whole concept of a limiting reagent is that if you react Xg of one substance with Yg of this substance how much is your max yield going to be for your reaction. If you're given a formula for the reaction you take the number of grams convert it to the number of moles and then see which reagent you don't have enough of to completely react the other. In your case according to your lab protocol you were supposed to take some known amount of Sodium bicarbonate and add drop wise HCl until the bubbling stopped, the bubbling happens as a result of CO2 gas leaving your reaction mixture.

Answer 14

ohhh.. i get it so there's no limiting reagent?

Answer 15

So I don't need to calculate for the moles?

Answer 16

Also there's no excess reagent?

Answer 17

Hard to calculate in your case cause you dumped extra acid in without taking the exact amount, normally you'd have said that in 4.56g of sodium bicarbonate you have 0.0542mole of bicarbonate and that the reaction has a ratio of 1/1 mol of bicarbonate to HCl, from there you say that M=mol/L so you had 0.0542moles HCl/25mL=2.168M although if you need to take into account sig figs it's 2.2M. And there isn't a reagent in excess, since you reacted every single gram of base with a drop of acid.

Answer 18

Ohh.. Sigh. I guess i should re-do the lab over again?

Answer 19

well you'll be off by a small margin, if you have the chance to redo and you are willing to then by all means but the percent by which you'll be off isn't that bad.