How many grams of sodium chloride must dissolve in 750.0 g of water to make a 0.50 molal solution?

Molality is defined as the number of moles of solute in 1 kg of solvent.
molality of solution to be prepared is 0.50 molal
this means that in 1000 g of water there should be 0.50 mol of NaCl
if 1000 g of water should contain - 0.50 mol 
then 750.0 g of water requires - 0.50 mol/kg x 0.750 kg = 0.375 mol
mass of NaCl in 0.375 mol - 58.5 g/mol x 0.375 mol = 21.9 g
therefore a mass of 21.9 g of NaCl is required 

Standing in the sunlight and feeling the heat on your face (uv radiation is entering the skin, converting to infrared radiation, and is absorbed by your tissues)orstanding near a fire and feeling the heat on your skin (infrared radiation transfer)

The main types of electromagnetic radiation. radio  waves have  the lowest frequencies  and  longest  wavelengths, while gamma  waves have highest frequencies  and shortest wavelengths. the wavelengths vary across the electromagnetic spectrum from about 10–15 m to more than 104 m.hope it !