How many ppm when add 10kg of chlorine 70% concentrated to 500 barrel of water

ppm means particles per million.

1 ppm is 1ug per cm^3, or 1mg per litres.

Now, I'm not sure what you are meaning with 10 kg of 70% concentration...
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10 kg of chlorine at 70% purity is 7 kg of pure chlorine.

This means you have 7 kg of chlorine in 500 barrels of water.

Depending on which system you use, the total volume of water will vary.

If you use the metric system, convert all the water to litres.

Then, you can use proportions to find the mass of chlorine in each litre of water.