In a double covalent bonds there are 4 valence electrons that are shared.
They react to form salt ZnCl + hydrogen gas
The researcher may first weight the beaker with water and then start to heat the water to a constant temperature, for example 30 °C and then start adding salt and stirring. He should add salt slowly until solid salt starts to become visible and the solution starts becoming cloudy. When this happens, he should quickly weigh the beaker. The increase in mass is the mass of salt dissolved at that temperature.
The procedure is then repeated but at an increased temperature until 5-6 temperatures have been tested.
Answer: In the chemical formula for water, the subscript for hydrogen is 2. Notice that the 2 is smaller and written slightly below the H and O. It is called a subscript because it is written ("script") "below" ("sub") the preceding letter.
Explanation:
