Answer:
pH = 4
Explanation:
pH = -log[H⁺] = -log(10⁻⁴) = -(-4) = 4
We have to get the stable atom formed after positron emission from Terbium-147.
The stable atom is (D) ₆₄Gd¹⁴⁷.
Positron is radioactive decay. Positron is a type of beta particle β⁺.
Positron emission decreases proton number relative to neutron number, positron decay results in nuclear transmutation, changing an atom of one chemical element with an atomic number that is less by one.
Terbium on positron emission produces Gadolinium with one atomic number less than Terbium. So, the positron emission reaction is as shown below:
Tb¹⁴⁷→ ₆₄Gd¹⁴⁷ + ₁e⁰
We are given the number of moles of solid magnesium supplied for the reaction which is 0.02 moles while hydrochloric acid is supplied in excess thus we can say that the reaction proceeds to completion. Calculation is as follows:
0.020 mol Mg ( 1 mol H2 / 1 mol Mg ) = 0.020 mol H2 gas is produced
To convert the number of moles to volume, we use the conditions at STP of 1 mol of a substance is equal to 22.4 L. Thus,
0.020 mol H2 (22.4 L / 1 mol) (1000 mL / 1 L) = 448 mL
It's a base because it increases the concentration of hydroxid ions
