A chemist must prepare of sodium hydroxide solution with a pH of at . He will do this in three steps: Fill a volumetric flask about halfway with distilled water. Weigh out a small amount of solid sodium hydroxide and add it to the flask. Fill the flask to the mark with distilled water. Calculate the mass of sodium hydroxide that the chemist must weigh out in the second step. Round your answer to significant digits.

The question is incomplete, the complete question is:

A chemist must prepare 0.9 L of sodium hydroxide solution with a pH of 13.40 at 25 C. He will do this in three steps: Fill a 0.9 L volumetric flask about halfway with distilled water. Weigh out a small amount of solid sodium hydroxide and add it to the flask. Fill the flask to the mark with distilled water. Calculate the mass of sodium hydroxide that the chemist must weigh out in the second step.

9g of NaOH

Explanation:

First, the POH must be obtained from the given pH so that we can use this POH to obtain the hydroxide ion concentration. When we obtain the hydroxide ion concentration, as shown in the image, we can now use it to find the mass of sodium hydroxide required to prepare the standard solution since we have the volume of the solution in liters and we can calculate the molar mass of sodium hydroxide to be 40gmol-1. All these steps are shown in the image attached.

answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"