The concentration of a hydrochloric acid solution is 0.5mol/dm3.

25cm^3 * 0.5mol/1000cm^3 = 12.5/1000 = 0.0125 mole

0.0125

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0.001 x 25 = 0.025 (conversion from cm3 to dm3)

mole = concentration x volume (solutions)
0.025 x 0.5 = 0.0125

Well, well, well! Looks like we have a chemistry question here, huh? Don't worry, I'm here to make chemistry a little less acidic with some humor!

To find the number of moles, we need to use the formula: Moles = Concentration x Volume.

So, let's put on our chemistry hats and crunch some numbers! The concentration is given as 0.5 mol/dm3 and the volume is 25 cm3. But wait, we need the volume in dm3 to keep our units consistent. Remember, chemistry likes everything to be in harmony!

So, 25 cm3 is equal to 0.025 dm3 (since 1 dm3 = 1000 cm3). Got it? Good!

Now, let's plug in the values:

Moles = 0.5 mol/dm3 x 0.025 dm3
Moles = 0.0125 mol

Voila! The answer is A) 0.0125 moles of hydrochloric acid. Time to celebrate with a little acid-free dance party!

Keep those chemistry questions coming! I'm ready to make them less mind-boggling and more giggly!

To find the number of moles of hydrochloric acid in 25 cm³ of the solution, we first need to convert the volume from cm³ to dm³ since the concentration is given in mol/dm³.

1 dm³ is equal to 1000 cm³, so we divide 25 cm³ by 1000 to convert it to dm³:
25 cm³ ÷ 1000 = 0.025 dm³

Now, we can use the given concentration of the solution to calculate the number of moles. The concentration of the hydrochloric acid solution is 0.5 mol/dm³.

Multiplying the concentration by the volume gives us the number of moles:
Number of moles = Concentration × Volume

Therefore, the number of moles = 0.5 mol/dm³ × 0.025 dm³ = 0.0125 mol

So, there are 0.0125 moles of hydrochloric acid present in 25 cm³ of the solution.

Therefore, the correct answer is A) 0.0125.