25cm cubes of potassium hydroxide was prepared by dissolving 11.2grams of potassium hydroxide in 250cm cubes of distilled water, was found to exactly neutralize 20cm cubes of a certain hydrochloric acid solution . Find the molarity of the acid in moles/dm cube and grams/dm cube
To find the molarity of the hydrochloric acid solution, we need to first determine the number of moles of potassium hydroxide (KOH) used.
Step 1: Calculate the number of moles of KOH:
The molar mass of KOH is:
K (potassium) = 39.10 g/mol
O (oxygen) = 16.00 g/mol
H (hydrogen) = 1.008 g/mol
Hence, the molar mass of KOH = (39.10 g/mol) + (16.00 g/mol) + (1.008 g/mol) = 56.10 g/mol
Given that 11.2 grams of KOH were used, we can calculate the number of moles as follows:
Number of moles = mass / molar mass
Number of moles = 11.2 g / 56.10 g/mol = 0.199 moles (rounded to three decimal places)
Step 2: Calculate the molarity of the hydrochloric acid solution:
In a neutralization reaction, the moles of the acid will be equal to the moles of the base.
According to the problem, 20 cm³ of the hydrochloric acid solution reacts with 25 cm³ of the potassium hydroxide solution.
Since the volumes of the solutions are in cubic centimeters (cm³), we need to convert them to cubic decimeters (dm³) before finding the molarity.
1 dm³ = 1000 cm³, so 20 cm³ = 20/1000 dm³ = 0.02 dm³
Similarly, 25 cm³ = 25/1000 dm³ = 0.025 dm³
Now we can calculate the molarity of the hydrochloric acid solution using the formula:
Molarity (M) = moles / volume (in dm³)
Molarity = 0.199 moles / 0.02 dm³ = 9.95 moles/dm³ (rounded to two decimal places)
Step 3: Convert molarity to grams/dm³:
To convert moles/dm³ to grams/dm³, we need to multiply the molarity by the molar mass of the acid.
The molar mass of hydrochloric acid (HCl) is:
H (hydrogen) = 1.008 g/mol
Cl (chlorine) = 35.45 g/mol
Hence, the molar mass of HCl = (1.008 g/mol) + (35.45 g/mol) = 36.458 g/mol
Grams/dm³ = Molarity (moles/dm³) x Molar mass (g/mol)
Grams/dm³ = 9.95 moles/dm³ x 36.458 g/mol = 362.15 g/dm³ (rounded to two decimal places)
Therefore, the molarity of the hydrochloric acid solution is 9.95 moles/dm³ and the concentration in grams/dm³ is 362.15 g/dm³.