To answer this question, we need more information.
To calculate the percent by mass of KBr in a saturated solution at 10 °C, we need to know the solubility of KBr at that temperature. The solubility of KBr in water varies with temperature. Without this information, we cannot provide an accurate calculation.
The solubility of KBr at 10 °C can be determined from experimental data or reference sources. Once the solubility is known, the percent by mass of KBr can be calculated using the formula:
Percent by mass of KBr = (mass of KBr / mass of solution) × 100
Where the mass of KBr is the mass of KBr dissolved in the given amount of water to form a saturated solution. The mass of the solution is the total mass of the solution, which includes the mass of both KBr and water.
Hope this helps.