Question

if i conduct a 1:5 dilution on a sample, then another 1:5 dilution of that dilution, how diluted is the second dilution relative to the original sample? 1:10 1:25 1:1 1:55 how much original sample would i include to make 600 ul total of a 1:100 dilution? 100 ul 6 ul 60 ul 60,000 ul

Explanation:

Step1: Calculate total dilution factor for first part

For a 1:5 dilution followed by another 1:5 dilution, the total dilution factor is the product of the two dilution - factors. The dilution factor for a 1:5 dilution is 5. So, the total dilution factor $D = 5\times5=25$. So the second - dilution is 1:25 relative to the original sample.

Step2: Calculate volume of original sample for second part

The formula for dilution is $C_1V_1 = C_2V_2$. In a 1:100 dilution, if the final volume $V_2=600$ $\mu$l and the dilution factor is 100 (i.e., $C_2=\frac{C_1}{100}$), then from $C_1V_1 = C_2V_2$, we can rewrite it as $V_1=\frac{C_2V_2}{C_1}$. Since $C_2=\frac{C_1}{100}$, then $V_1=\frac{V_2}{100}$. Substituting $V_2 = 600$ $\mu$l, we get $V_1 = 6$ $\mu$l.

Answer:

1. B. 1:25
2. B. 6 $\mu$l