Answer:
6
Explanation:
The number of hydrogen atoms in the given compound is 6 atoms.
Given compound is:
3H₂CO₃
An atom is the smallest indivisible particles of an element.
In the compound;
3H₂CO₃
Elements Number of atoms
H 3(2) = 6
C 3(1) = 3
O 3(3) = 9
The number of hydrogen atoms in the compound is 6
There is no gaseous product when NaNO3 reacts with 6M HCl.
We must note that gas evolution is one of the signs that a chemical reaction has taken place. Hence, we must consider the options and look out for an option in which reaction with HCl does not lead to a gaseous product. This is the option that does not lead to evolution of a gas.
Let us consider the reaction; NaNO3(s) + HCl(aq) ---> NaCl(s) + HNO3(aq), there is no gaseous product hence NaNO3 does not result in gas evolution upon addition of 6M HCl.
Missing parts;
Addition of 6 M HCl to which substance will NOT result in gas evolution?
(A) Al
(B) Zn
(C) K2CO3
(D) NaNO3
Learn more about evolution of gas: brainly.com/question/2186340
Answer: 1. C. polar covalent: electrons shared between silicon and sulfur but attracted more to the sulfur
2. B) 
3. B) Fluorine
Explanation:
1. A polar covalent bond is defined as the bond which is formed when there is a difference of electronegativities between the atoms.
Electronegativity difference = electronegativity of sulphur- electronegativity of silicon = 2.5 -1.8 = 0.7
Thus as electronegativity difference is less than 1.7 , the cond is polar covalent and as electronegativity of sulphur is more , the electrons will be more towards sulphur.
2. A molecular compound is usually composed of two or more nonmetal elements. Example:
Ionic compound is formed by the transfer of electrons from metals to non metals. Example:
,
and 
3. For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.
Here K is having an oxidation state of +1 and as the compound formed is KZ, the oxidation state of non metallic element Z should be -1. Thus the element Z is flourine which exists as diatomic gas 
The answer is B. Decreasing the cylinder volume decreases the amount of space the gas has to occupy there for increasing pressure