[Johulus]

After electrolysis of sodium nitrate aqueous solution the mass fraction of sodium nitrate was 60%. The mass fraction of sodium nitrate before electrolysis was 40%. What is the overall volume of gasses produced during the electrolysis at temperature of 20°C and pressure of 99.8 kPa?

I don't know how to start. I'm lost. Everything would be fine if I had masses but I don't know what should I do with just fractions. 

[Borek]

Not enough data to solve. The only thing you can do is to report the answer as "x L per 1000 g of the initial solution".

[Johulus]

Thanks! That's what I thought but I was so confused. It's all info that was provided in the task. Weird.

[Hunter2]

Additional you can calculate the Percentage of the water what was electrolysied. Its 33,3...%.

With an given start volumen or start mass its possible. to calculate the rest.

[Johulus]

Actually I have a result also and it should be 169.2. It seems they calculated the volumes of gasses for 100g of sodium nitrate. Thank you on your answers.