The density of the sample is:
Density = mass / volume
Density = 9.85 / 0.675
Density = 14.6 g/cm³
If the sample has 95% gold, and 5% silver, its density should be:
0.95 x 19.3 + 0.05 x 10.5
Theoretical density = 18.9 g/cm³
The difference in theoretical and actual densities is very large, making it likely that the jeweler was not telling the truth.
A balanced chemical reaction obeys the law of conservation of mass, because the same number of atoms of each element must appear on both sides of the equation for the reaction … , and in any actual reaction, the same exact atoms will be found on both sides of the equation.
Mass of Hydrogen gas required to react : 0.936 g
<h3>Further explanation</h3>
Reaction on Nitrogen gas and Hydrogen gas to produce Ammonia gas
N₂ (g) + 3 H₂ (g) ⇒ 2 NH₃ (g)
Conditions at T 0 ° C and P 1 atm are stated by STP (Standard Temperature and Pressure). At STP, Vm is 22.4 liters / mol
so mol Nitrogen for 3.5 L at STP :

From the equation, mol ratio of N₂ : H₂ = 1 : 3, so mol H₂ :

then mass of Hydrogen(MW= 2 g/mol) :

Answer:
I'd say it's the number of water drops.
Explanation:
The number of water drops is what you're controlling or purposely controlling and that answer choice makes the most sense out of the other answer choices. So I'd say it's "The Number of Water Drops."