Pick the correct statement for the following isotope: a. 42Ca 42 is the mass number and 20 is the atomic number. b. 42 is the nu
mber of neutrons and 20 is the number of protons. c. 42 is the number of protons and 20 is the number of electrons. d. 42 is the atomic number and 20 is the number of neutrons.
To label an element correctly using a combination of the symbol, mass number and atomic number furnishes some important information about the element.
We can obtain these information from the element provided that correct labeling of the element is presented. Firstly, after writing the symbol of the element, the atomic number is placed as a subscript on the left while the mass number of the atomic mass is placed as a superscript on the same left.
Looking at the question asked, we have the element symbol in the correct position as Ca, with 42 also in the correct position which is the mass number. The third number which is 20 is thus the atomic number of the element.
The balanced equation for the neutralisation reaction is as follows Ca(OH)₂ + H₂SO₄ ---> CaSO₄ + 2H₂O stoichiometry of Ca(OH)₂ to H₂SO₄ is 1:1 equivalent number of acid reacts with base number of H₂SO₄ mol reacting - 2 mol according to molar ratio of 1:1 number of Ca(OH)₂ mol = number of H₂SO₄ moles therefore number of Ca(OH)₂ moles required - 2 mol