Answer: The beaker in which water level has decreased more is the one that contains pure water.
Explanation: Even when water is not heated it can evaporate, that is because molecules move at different speed and those that are closer to surface can break the gass pressure and scape as water vapor.
The movement of molecules of water can be affected by the presence of solutes (salts or other soluble compounds) and increase the evaporation temperature. For this particular case, molecules of salt atract the water molecules (remember salt has ions and water is a dipole with partial charges) and do not let the water move freely which avoid them to scape to the surface.
1) Chemical reactions produce new substances
Ans (d)
2) The symbol, Δ in a chemical reaction means that heat of supplied to the reaction.
Ans (a)
3) A skeleton equations does not show the reaction stoichiometry, i.e. the relative amounts of reactants and products.
Ans (d)
From what I would think, it is D.
Given:
Atomic radius of gold = 144 x 10⁻¹² m = 144 pm
Density of gold = 19.3 g/cm³ = 19.3 x 10⁻³ kg/cm³
Mass of gold sample = 1.40 g = 1.4 x 10⁻³ kg
Calculate the volume of an atom.
v = [(4π)/3]*(144 x 10⁻¹² m)³ = 1.2508 x 10⁻²⁹ m³
Calculate the mass of an atom.

Calculate the number of atoms in a sample of mass 1.40 g.

Answer: 5.8 x 10²¹ atoms