Answer:
i) Protons and neutrons
ii) Mass number = 15
iii) Atomic number= 12
Explanation: i) The atom is composed of two parts: named as nucleus which contains neutrons and protons which contributes to most of the mass and there is extra nuclear part which consists of electrons which revolve around the nucleus. Thus subatomic particles are found in the nucleus of the atom are protons with positive charge and neutrons with no charge.
ii) Atomic number is equal to the number of protons or the number of electrons for a neutral atom and is specific to a particular element.
Mass number is the sum of number of protons and the number of neutrons.
Given : atomic number of oxygen = 8 = number of protons
Number of neutrons = 7
Thus mass number = number of protons + number of neutrons = 8+7= 15.
iii) Mass number = 25
Number of neutrons = 13
Mass number = number of protons + number of neutrons
25 = number of protons + 13
number of protons= 25-13 = 12
Thus atomic number = number of protons = 12
Answer:
As more sodium chloride is dissolved, higher is the boiling point of the solution
Explanation:
The boiling point- the temperature at which the solution boils- will increase as more solute is added. That is a colligative property called <em>boiling point elevation</em>. Colligative propeties are those that depend on the number of particles of solute in a solution. As more solute is added (sodium chloride or NaCl), more particles of solute will be present in the solution and the boiling point of the solution will be higher. The mathematical expression for the boiling point elevation (ΔTb) is the following:
ΔTb= Kb x m
Where Kb is a molal constant and m is the molality of the solution. That expression shows that the elevation of boiling point depends on the concentration of the solute expressed in terms of moles per mass of solution.
Explanation:
The law of conservation of mass and energy according to thermodynamics is NOT violated. The ash of the wood weighs less than the initial wood because during the burning some of the mass was converted to gases that escaped into the atmosphere. Some of the carbon in the wood, for example, turned to carbon dioxide. Water in the wood also turned to gas (water vapour) and escaped.
If it is possible to capture all these gases and weigh them, then ideally it would be observable that the law of conservation is NOT violated.