The reaction between calcium carbonate and hydrochloric acid can be expressed through the chemical reaction,
CaCO3 + 2HCl --> CaCl2 + H2O + CO2
The molecular weight of calcium carbonate is 100 g/mol while that of hydrochloric acid is 36.45. The equation above depicts that 100 g of calcium carbonate can be dissolved in 72.9 g of hydrochloric acid.
x = (4 g HCl)(100 g CaCO3 / 72.9 HCl)
x = 5.49 g
Answer: 5.49 g
1. No two elements have the same kind of atom.
Explanation:
The correct of all statement is that no two elements have the same kind of atoms.
Every element have different atoms.
- Over a hundred elements have been identified by scientists.
- Atoms are the smallest particles that takes part in chemical reactions.
- Elements are distinct substances that cannot be split.
- Atoms of all elements do not have the same mass and volume. Isotopes are examples.
- It is true that atoms of all elements have different masses and also different volumes.
- The volume of an atom is function of the number of electrons it contains.
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D. Is a fly shot effective in preventing the flu?
Answer A touches on the topics of economics and industrial feasibility of the flu shot.
B is more of an ethical / situational question.
C is a social question.
D is the only question which focuses on the science of microbiology and medicine.
Answer:
Ammonia is the richest source of nitrogen on a mass percentage basis because it has 82.35% of nitrogen by mass.
Explanation:
Percentage of element in compound :

(a) Urea, 
Molar mass of urea = 60 g/mol
Atomic mass of nitrogen = 14 g/mol
Number of nitrogen atoms = 2

(b) Ammonium nitrate, 
Molar mass of ammonium nitrate = 80 g/mol
Atomic mass of nitrogen = 14 g/mol
Number of nitrogen atoms = 2

(c) Nitric oxide, NO
Molar mass of nitric oxide = 30 g/mol
Atomic mass of nitrogen = 14 g/mol
Number of nitrogen atoms = 1

(d) Ammonia, 
Molar mass of ammona = 17 g/mol
Atomic mass of nitrogen = 14 g/mol
Number of nitrogen atoms = 1
Ammonia is the richest source of nitrogen on a mass percentage basis because it has 82.35% of nitrogen by mass.
Newton first law of motion
Explanation:
This law by Newton states that an object will remain at rest, or a moving object will stay in motion in a straight line and with the same speed unless an external and unbalanced force acts on the object.
One application of this Newtonian law is in the launching of projectiles like ballistic missiles. A ballistic missile parabolic path is affected by its inertia and the unbalanced forces acting on the object such as air resistance/ drag and gravity.