When preparing a 10% bleach disinfectant solution, what is the correct ratio of water to bleach?

The correct choice involves combining 90 ml of water with 10 ml of bleach, resulting in a solution that contains 10% bleach. This means that the final volume of the solution is 100 ml, where the bleach constitutes 10% of the total volume.

To obtain a 10% solution, you need to ensure that the amount of bleach is one-tenth of the total volume of the solution. Since you are using 10 ml of bleach, adding 90 ml of water brings the total volume to 100 ml. This accurately represents the desired concentration.

In contrast, the other options either do not maintain the appropriate ratio or result in concentrations that exceed 10%. For instance, using more water with less bleach would dilute the solution too much, whereas using a larger volume of bleach would increase the concentration beyond the target of 10%. Understanding the proper ratios is crucial for preparing effective disinfectants while ensuring safety and efficacy in infection control practices.