concentration calculations

The concentration of a bottle of hydrochloric acid is 73 g/dm³. What is the mass of HCl in 2 dm³ of this bottle of acid?

14 g of potassium hydroxide was dissolved in water to form 0.1 dm³ of an aqueous solution. What was the concentration of this KOH solution in mol/dm³?

80g of sodium hydroxide, NaOH, was dissolved in 1dm³ of water.

    Calculate the concentration of the solution in mol/dm³

4g of sodium hydroxide, NaOH, was dissolved in 250cm³ of water.

     Calculate the concentration of the solution in mol/dm³.

CaCO₃(s)    -->    CaO(s)    +    CO₂(g)

Limestone (CaCO₃) decomposes according to the equation above.

During the decomposition process, 3dm³ of carbon dioxide is collected. Calculate the mass of limestone decomposed.

Hydrogen peroxide, H₂O₂, decomposes to give oxygen gas and water.

2H₂O₂(aq)   -->  2H₂O(l)    +   O₂(g)

Given that 50cm³ of 2mol/dm³ of hydrogen peroxide is decomposed

calculate the volume of oxygen gas evolved in cm3