Which metal could you use to reduce Cr3+ ions but not Mn2+ ions?

Answer: 0.0164 molar concentration of hydrochloric acid in the resulting solution.

Explanation:

1) Molarity of 0.250 L HCl solution: 0.0328 M

The amount of HCl in the 0.250 L solution = 0.0082 moles

2) Molarity of 0.100 L NaOH solution: 0.0245 M

The amount of NaOH in the 0.100 L solution = 0.00245 moles

3) Determining the concentration of hydrochloric acid in the final solution.

0.00245 moles of NaOH will neutralize 0.00245 moles of HCl from the original 0.0082 moles of HCl.

The total volume of the mixture becomes 0.100 L + 0.250 L = 0.350 L

Remaining moles of unreacted HCl = 0.0082 moles - 0.00245 moles = 0.00575 moles

Concentration of the remaining HCl:

0.0164 molar concentration of hydrochloric acid in the resulting solution.

Answer: D) X-rays exhibit lower frequency than microwaves

Explanation:

A scientific statement is one that relies on evidence gathered from experiments and direct observation of the natural world. Such a statement can be corroborated through appropriate experimental methods.

The option D illustrates a scientific statement because it allows for the frequency of both microwaves and X-rays to be assessed and contrasted. This process entails experimental and observational techniques, which validates it as a scientific statement.