======Effect of Particle Size Acid and Marble Chips======


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**Alternative titles:** Marble Chips and HCl Surface Area Effect
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====Summary====                   
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====Procedure====  
  -Gather a conical flask, top-loading balance, dilute hydrochloric acid of fixed concentration, three marble chip size ranges (same total mass for each run), cotton wool, timer, and graph paper or spreadsheet.
  -Place a measured volume of the acid in the flask and set the flask on the balance; insert a loose cotton-wool plug to reduce spray while allowing gas to escape. Tare the balance to 0.00 g.
  -Start the timer, quickly add the preweighed marble chips (smallest size first), replace the cotton plug, and record mass every 5–10 s until the mass change per interval becomes very small.
  -Repeat the run with the same acid volume and concentration, the same marble mass, and the same temperature, but with medium-sized chips, then large chips.
  -Plot “mass of CO2 produced” versus time (mass loss from 0.00 g). Draw a best-fit curve for each chip size.
  -Note that with the same acid volume and concentration, all runs should approach the same total CO2 at long times, even though the initial rates differ.



====Links==== 
The Effect of Surface Area on Reaction Rate - Rugby School Chemistry: 
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Effect of Surface Area on the Rate of Reaction | Chemistry Practicals - Science with Hazel: 
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📄 The effect of surface area on the rates of chemical reactions - Chemguide: Core Chemistry: [https://www.chemguide.uk/14to16/rates/surface.html]]\\

====Variations====
  *Collect CO2 with a gas syringe or inverted buret and compare initial volumes per second instead of mass loss.
  *Hold surface area constant and vary acid concentration to compare how concentration and surface area each affect initial rate.
  *Use powdered CaCO3 versus large lumps to illustrate an extreme surface area change; shorten sampling intervals for powder.
  *Investigate stirring or gentle swirling as a mass-transfer variable; keep all other conditions constant.



====Safety Precautions====
  *Wear splash goggles, lab coat, and appropriate gloves; tie back hair and secure loose clothing.
  *Hydrochloric acid is corrosive; avoid skin and eye contact and rinse spills with plenty of water.
  *Do not seal the flask; CO2 must vent freely. Use only a loose cotton-wool plug to limit spray.
  *Handle marble dust carefully; avoid inhalation if using finely divided CaCO3.
  *Keep glassware stable on the balance; protect the balance with a tray in case of spills.
  *Wash hands after the experiment and remove gloves before touching shared equipment.




====Questions to Consider====
  *Why do smaller chips react faster than larger chips of the same total mass? (They provide more surface area, so more CaCO3 particles are exposed for collisions with H+ at any moment.)
  *Why do all curves level off at roughly the same total CO2 for a fixed acid volume and concentration? (The acid is the limiting reagent; once H+ is consumed, the reaction stops regardless of chip size.)
  *Why use the initial rate rather than the whole curve to compare conditions? (At t = 0 the concentrations and temperature are best defined; later, changes make comparisons less fair.)
  *How does the cotton-wool plug improve data quality in the mass-loss method? (It reduces liquid spray loss while still letting CO2 escape, so mass loss mostly reflects gas release.)
  *What controlled variables are essential here? (Acid concentration and volume, total CaCO3 mass, temperature, mixing, and sampling interval.)
  *If you switched to gas collection, what units would you use for rate and how would you find the initial rate? (cm³ s⁻¹; draw a tangent at t = 0 to find the initial slope of volume vs time.)