Question

Experimental RecordFlaskMass ofCalcium CarbonateVolume ofHClVolume ofWaterTime14.0 g25 mL0 mL11.2 seconds24.0 g20 mL5 mL34.0 g15 mL10 mL44.0 g10 mL15 mLBased on your knowledge of factors that affect the rates of chemical reactions, predict the trend in the last column of the experimental record. Use complete sentences to explain the trend you predicted. You do not have to determine exact values for time; just describe the trend you would expect (increase or decrease) and why it occurs.

Answer 1

We know that the rate of a chemical reaction depends, among other factors, on the initial concentration of the reagents.

As we can see, at first, the time was studied when there was only hydrochloric acid and calcium carbonate, and the concentration of the acid was 100%.

Then, in the experimental record it was changed the amount of water and acid in the reaction, decresing the concentration of this substance.

If the concentracion of hydrochloric acid is decreasing due to the increase of water in the reaction, the rate of chemical reaction will decrease, resulting in longer reaction times.

It means that the trend in the last column will be an increasing behaviour in the time due to the decrease of the rate of reaction.