Dilution Equation: M?V? = M?V?
The dilution equation M?V? = M?V? states that the number of moles before and after dilution remains constant. M is molarity, V is volume, and subscripts 1 and 2 denote initial and final states. This simple but powerful equation helps calculate the volume or concentration after dilution. For example, to dilute 10 mL of 2 M solution to 0.5 M: (2)(10) = (0.5)(V?), giving V? = 40 mL. Add 30 mL of solvent to the original 10 mL.
Performing Dilutions Correctly
Proper dilution technique is crucial for accuracy. Always add concentrated solution to solvent, never vice versa, especially for acids to prevent dangerous splattering and heat generation. Use volumetric glassware for precision. For serial dilutions (repeated dilutions), multiply dilution factors. A 1:10 dilution repeated three times gives 1:1000 overall. Mix thoroughly after each addition. Temperature affects volume, so prepare solutions at working temperature. Understanding dilution prevents waste and ensures experimental accuracy.
Applications in Labs
Dilution is routine in chemistry, biology, and medical labs. Biologists dilute bacterial cultures to countable concentrations. Clinical labs dilute blood samples for analysis. Chemists prepare standard solutions from concentrated stock. Pharmacists compound medications at specific concentrations. Environmental scientists dilute samples to detectable ranges. Dilution allows handling of concentrated materials safely and economically. Stock solutions save time and reduce weighing errors-one accurate preparation serves many dilutions.
Quick Tips
- Always verify units are consistent
- Use scientific notation for very large/small numbers
- Results are approximations — real conditions may vary
Frequently Asked Questions
Dilution factor is the ratio of final to initial volume (V?/V?) or initial to final concentration (M?/M?). A 1:10 dilution means dilution factor of 10. Multiply successive dilution factors for serial dilutions.
Mix 1 part concentrated solution with 9 parts solvent to get 10 parts total. For example, add 1 mL of solution to 9 mL of water for 10 mL final volume at 1/10th the original concentration.
No, dilution always decreases concentration by adding solvent. To increase concentration, you must evaporate solvent or add more solute. The term 'dilution' specifically means making less concentrated.
Adding acid to water distributes heat safely. Adding water to concentrated acid can cause violent boiling and splattering due to the large heat of dilution. Always remember: 'Do like you oughta, add acid to water.'
Serial dilution involves sequential dilutions, each using the previous dilution as starting material. A series of 1:10 dilutions (10??, 10?^2, 10?^3...) creates a wide range of concentrations efficiently.