Final answer:
To calculate the mole per dm³ of an acid from its percentage by mass, specific gravity, and molar mass, multiply the specific gravity by 1000 to find the mass of 1 dm³ of solution, calculate the mass of the acid, and then divide by the molar mass to find the number of moles. For the given 56% by mass and 1.25 specific gravity acid with a molar mass of 70g, the concentration is 10 moles per dm³.
Step-by-step explanation:
To find the mole per dm³ of an acid given its percentage by mass, specific gravity, and molar mass, we follow these steps:
- Calculate the mass of the acid in 1 dm³ of the solution using the percentage by mass and the specific gravity.
- Convert the mass of the acid to moles using the molar mass.
In this case, the specific gravity of the acid is 1.25, which means that 1 dm³ (which is equivalent to 1 liter) of the acid weighs 1.25 kg (since specific gravity is a ratio of the substance's density compared to the density of water and 1 liter of water weighs 1 kg). Since the acid is 56% by mass, 1 dm³ of this solution contains 700 g of acid (56% of 1250 g).
Now, using the molar mass of the acid, which is 70 g/mol, we can find the number of moles in 700 g:
Moles = mass (g) / molar mass (g/mol) = 700 g / 70 g/mol = 10 moles.
Therefore, the concentration of the acid in the solution is 10 moles per dm³.