the answer is option D "people emphasized obtaining knowledge through scientific experiments" (on plato)
I believe the answer is "After adding two substances together a new order is detected" because nearly all of the other answers suggest a chemical change has taken place. The reason I say "almost" is because answer two and four results in bubbles forming so the answer cannot be both. The only one to not clearly show a chemical change has occurred is the last answer.
The reaction is:
2 NO₂ (g) + F₂ (g) ⇆ 2 NO₂F (g)
The stoichiometric coefficients of the substances balance out each other to obey the Law of Definite Proportions. Now, you have to note that determining the reaction rate expression is specific to a certain type of reaction. So, this are determined empirically through doing experiments. But in chemical reaction engineering, to make things simple, you assume that the reaction is elementary. This means that the order of a reaction with respect to a certain substance follows their individual stoichiometric coefficients. What I'm saying is, the stoichiometric coefficients are the basis of our reaction rate orders. For this reaction, the rate order is 2 for NO₂, 1 for F₂ and 2 for NO₂F. When the forward and reverse reactions are in equilibrium, then it applies that:
Reaction rate of disappearance of reactants = Reaction rate of formation of products.
Therefore, we can have two reaction rate constants for this. But since the conditions manipulated are the reactant side, let's find the expression for reaction rate of disappearance of reactants.
-r = k[NO₂]²[F₂]
The negative sign before r signifies the rate of disappearance. If it were in terms of the product, that would have been positive. The term k denotes for the reaction rate constant. That is also empirical. As you can notice the stoichiometric coefficients are exponents of the concentrations of the reactants. Let's say initially, there are 1 M of NO₂ and 1 M of F₂. Then,
-r = k(1)²(1)
-r = k
Now, if we change 1 M of NO₂ by increasing it to its half, it would now be 1.5 M NO₂. Then, if we quadruple the concentration of F₂, that would be 4 M F₂. Substituting the values:
-r = k(1.5)²(4)
-r = 9k
So, as you can see the reaction rate increase by a factor of 9.
Answer:- 0.88
Solution:- Masses of silver and copper metals are given and we are asked to calculate the percentage of silver in the alloy.
mass percent of Ag = 
Mass of Ag = 17.6 g
mass of Cu = 2.40 g
mass of alloy = 17.6 g + 2.40 g = 20.0 g
Let's plug in the values in the formula:
mass percentage of Ag = 
mass percentage of Ag = 88%
So, the mass percentage of silver in sterling silver is 88% and in decimal form it is 0.88.
