Why must chromosomes be copied before cells divide

Under normal conditions, describe how increasing the temperatures effects the solubility of a typical salt

A50.0 ml sample of gas at 20.0 atm of pressure is compressed to 40.0 atm of pressure at constant temperature. what is the new volume? 0.0100 ml 0.325 ml 25.0 ml 100. ml

If you burn 46.6 g of hydrogen and produce 416 g of water, how much oxygen reacted