Answer:
D
Explanation:
The unit used to measure atomic mass is the atomic mass unit (amu). A single amu is equivalent to 1/12 the mass of an atom from the carbon-12 isotopIsotopes with different numbers of protons and neutrons will have an actual mass slightly different from the atomic mass calculated in atomic mass units.
Answer: The correct option is A.
Explanation: In a chemical reaction, reactants react to form a number of products.
For the formation of products, the bonds of the individual reactants must be broken and the bonds of the products must be formed.
For example: Formation of water from hydrogen gas and oxygen gas. Reaction follows:

The Bonds of hydrogen and oxygen molecule are broken and new bonds between hydrogen and oxygen atoms are formed to give water molecule.
Answer:
hen the number of neutrons is known and the atomic number of an element is known, it becomes easier to determine the approximate mass number by adding the two.
Explanation:
Hope it shelps
Answer:
A. There was still 140 ml of volume available for the reaction
Explanation:
According to Avogadro's law, we have that equal volumes of all gases contains equal number of molecules
According to the ideal gas law, we have;
The pressure exerted by a gas, P = n·R·T/V
Where;
n = The number of moles
T = The temperature of the gas
R = The universal gas constant
V = The volume of the gas
Therefore, given that the volumes and number of moles of the removed air and added HCl are the same, the pressure and therefore, the volume available for the reaction will remain the same
There will still be the same volume available for the reaction.