<h3>
Answer:</h3>
28.17 %
<h3>
Explanation:</h3>
In the question we are required to determine the percent by mass of nitrogen in (NH₄)₃PO₄.
- To calculate the percent by mass of an element in a compound we use the formula;
- % by mass =(Mass of the element÷ Relative formula mass of the compound)100
In this case;
- Atomic mass of nitrogen is 14.0 g/mol
But; There are three nitrogen atoms in (NH₄)₃PO₄.
Therefore; Mass of nitrogen in (NH₄)₃PO₄ = 14.0 × 3
= 42 g
The relative formula mass of (NH₄)₃PO₄ = 149.0867 g/mol
Thus;
% by mass of N = (42 g ÷ 149.0867 g/mo)× 100%
= 28.17 %
Therefore, the % by mass of N is (NH₄)₃PO₄ is 28.17%
<u>Answer:</u> The element having similar chemical properties that of calcium present in period 3 is magnesium.
<u>Explanation:</u>
In a periodic table, elements are arranged in 18 vertical columns known as groups and 7 horizontal rows known as periods.
Elements arranged in a group show similar chemical properties because of the presence of same number of valence electrons.
We are given:
Calcium is the 20th element of the periodic table having electronic configuration 
It has 2 valence electrons.
The element present in period 3 and have the same number of valence electron or in the same group is magnesium.
Hence, the element having similar chemical properties that of calcium present in period 3 is magnesium.
The mass, in grams, of hydrogen that would be produced from the reaction will be 0.102 grams
<h3>Stoichiometric calculations</h3>
From the balanced equation of the reaction:

The mole ration of magnesium to water is 1:2.
Mole of 4.73 grams Mg = 4.73/24.3 = 0.195 moles
Mole of 1.83 grams water = 1.83/18 = 0.102 moles
Hence, water is limiting.
Mole ratio of water to the hydrogen produced = 2:1
Equivalent mole of hydrogen gas produced = 0.102/2 = 0.05 moles
Mass of 0.05 moles hydrogen gas = 0.05 x 2 = 0.102 grams
More on stoichiometric calculations can be found here: brainly.com/question/27287858
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Answer:VO(ClO4)3 i'm sure this is it
Explanation:
I believe that would be a decomposer