Serial Dilution Quiz

Explanation
When performing a dilution, you mix a substance with a solvent to decrease its concentration. A 1:4 dilution means that you add 1 part of the substance to 4 parts of the diluent. In this case, if you've taken 250 µl of plasma and added 750 µl of distilled water, you have a total volume of 1000 µl. The dilution factor is calculated by dividing the total volume after dilution by the initial volume of the substance. Here, the dilution factor is 1000 µl ÷ 250 µl = 4, indicating a 1:4 dilution, making the statement True.

Explanation
The given statement is true because in a serial dilution, a small amount of the original solution is added to a larger amount of diluent to create a less concentrated solution. In this case, 100 ul of plasma is added to 900 ul of distilled water, resulting in a total volume of 1000 ul and a dilution factor of 1:10.

Explanation
The given statement is false because taking 20 ul from tube 1's 1:10 dilution and adding 80 ul of distilled water would actually achieve a 1:5 dilution for tube 2, not a 2:100 dilution.

Explanation
The explanation for the given correct answer is that a 1:10 dilution means taking 1 part of the original solution and adding 9 parts of the diluent (in this case, distilled water). So, by taking 100 ul (which is 1/10th of 1000 ul) from tube 1's 1:10 dilution and adding 900 ul of distilled water, we are effectively diluting the solution by a factor of 10 again. This results in a final dilution of 1:100 for tube 2. Therefore, the statement is true.

Explanation
A dilution is calculated by dividing the volume of the solute by the total volume of the solution. In this case, the volume of the solute (plasma) is 500 ul and the total volume of the solution after adding distilled water is 500 ul + 750 ul = 1250 ul. Therefore, the dilution would be 500 ul / 1250 ul, which simplifies to 2:5, not 7:4. Hence, the correct answer is false.

Explanation
The given statement is false. A 5:10 dilution means that the concentration of the substance is being reduced by a factor of 10. However, in tube 1, the plasma is being diluted by a factor of 10 (450 ul of distilled water) and not by a factor of 5. Therefore, the correct answer is false.

Explanation
The given statement suggests that the dilution in tube #5 is 1:100,000, assuming that tube #1 is a 1:10 dilution. This means that the concentration of the substance being diluted in tube #5 is 100,000 times lower than in tube #1. Therefore, the statement is true.

Explanation
The statement is false. The test does not need further dilution because the dilution has already been done correctly. The 80 ul of plasma diluted with 170 ul of distilled water resulted in a 1:4 dilution. Then, taking 200 ul of the 1:8 dilution and adding 100 ul of distilled water does not change the dilution factor. Therefore, the result does not need to be multiplied by 17.

Explanation
The statement is false because a 4:2 dilution ratio would mean that you have added 4 parts of plasma to 2 parts of distilled water. However, in this case, you have added 200 ul of distilled water to 250 ul of plasma, which is not a 4:2 ratio. Therefore, the statement is incorrect.

Explanation
The initial dilution of 1:4 means that the concentration of the plasma has been reduced by a factor of 4. However, the test still reads as needing further dilution, indicating that the concentration is still too high. By adding an additional 100 ul of distilled water to the 1:4 dilution, the concentration of the plasma is further reduced by a factor of 2. Therefore, the final dilution is 1:8 (4 x 2), and to obtain the actual concentration of the plasma, the result needs to be multiplied by 8. Therefore, the answer is true.