Answer: Protons
WHY?
Changing electrons will only result in the same element having different charges and hence, changing it's chemical properties.
Changing neutrons will not change an element but it will result in an isotope forming instead. (Isotopes are elements of the same type with different neutron numbers.)
However, changing the proton number would immediately change the nucleus composition, resulting in a change in element with a negative charge as there are more electrons than protons. This results in a expansion in valance electrons's distance from the nucleus. This results in a change in chemical properties of the element.
Therefore, a change in Protons is the answer.
From the equation, we see that the molar ratio of Fe : S required is:
8 : 1
The moles of Fe present are: 9.42/56 = 0.168
Moles of S = 68/(32 * 8) = 0.265
The molar ratio is:
1 : 1.6
Therefore, iron is the limiting reactant as it is present in a ratio lower than that required. The ratio of
Fe : FeS is
1 : 1
So 0.168 moles of FeS will form. The mass of FeS will be:
Mass = 0.168 * (56 + 32)
Mass = 14.78 grams
14.78 grams of FeS will be formed.
Answer:
10 kilowatts or 10,000 kw
Explanation:
Power = Force × Velocity
Given that:
Velocity of car is 50 m/s
The force is 200N
The power would be:
P = 200 × 50
P = 10,000 W
Notice that it only reaches watts because of the unit of the velocity is m/s. Standard unit to make Kw is km.
Since:
1 kw = 1000 w
10 kw = 10000 w
Credits to the person below me for correction.
Answer : The value of
for the final reaction is, 
Explanation :
The following equilibrium reactions are :
(1)

(2)

(3)

The final equilibrium reaction is :

Now we have to calculate the value of
for the final reaction.
First half the equation 1, 2 and 3 that means we are taking square root of equilibrium constant and then add all the equation 1, 2 and 3 that means we are multiplying all the equilibrium constant, we get the final equilibrium reaction and the expression of final equilibrium constant is:

Now put all the given values in this expression, we get :


Therefore, the value of
for the final reaction is, 
Formic acid when in water would dissociate into ions just like any acids. It would dissociate into the hydrogen ion and the formate ion. The equilibrium dissociation equation would be written as:
<span>HCOOH (aq) + H2O (l) ⇌ H+ (aq) + HCOO- (aq)
Formic acid is a weak acid which means that when in aqueous solution it does not completely dissociate into its corresponding ions. Only a certain amount that would be dissociated so in the solution there will be HCOOH, HCOO- and H+ molecules. It is also known as Methanoic acid and an important substance for the synthesis of a number of substances. It is naturally occurring in ants.</span>