Which of the following correctly converts a concentration of 25 millimolar (mM) to molar (M)?

• A. 0.25 M
• B. 0.0025 M
• C. 0.025 M
• D. 2.5 M

Answer: (C)

Verified step by step guidance

1. Understand the units involved: millimolar (mM) means millimoles per liter, and molar (M) means moles per liter.
2. Recall the conversion factor: 1 millimolar (mM) is equal to 1 \times 10^{-3} molar (M), because 'milli' means one-thousandth.
3. Set up the conversion by multiplying the given concentration in millimolar by the conversion factor: \$25\ \text{mM} \times \frac{1\ \text{M}}{1000\ \text{mM}}$.
4. Simplify the expression by dividing 25 by 1000 to convert millimolar to molar: \(\frac{25}{1000}\ \text{M}\).
5. Express the final concentration in molar units, which will be a decimal less than 1, representing the correct conversion.