In one or two sentences, explain why the combined weight of several liquids mixed in an open flask can be less than but never more than the sum of all the weights of the ingredients.

The law of conservation of mass states that mass is neither created or destroyed, so the combined mass of all the products after the reaction will be the same as the mass of all the reactants and never more, but since the flask is not closed, the gases produced from the reaction will move into the atmosphere and the product left behind , the solids and/or liquids, will be the only products that you’ll end up weighing, meaning it’ll be less weight than the original reactants. The reason I’m interchanging weight and mass is because although weight changes with gravity, so long as the gravitational force stays constant throughout the experiment, it’s pretty much the same.

Explanation:

choice d. The first reaction is a first order reaction, the second one should have an order greater than first.

Explanation:

1) Reaction 1:

It is stated that reaction 2 has a constant half-life time.

Constant half-life time is a characteristic of first order reactions.

This fact is derived from:

r =  k [A] - d[A] / dt = k[A] - d[A] / [A] = k dt- ln [A/Ao] = k tHalf-life ⇒ [A / Ao] = (1/2) - ln (1/2) = k t (half - life) ⇒ t (half-life) = ln (2) / k Since, ln (2) / k is a constant, t (jalf-life) is a constant.

So, the first conclusion is that the first reactions is a first order reaction.

2) Reaction 2.

It is stated that reaction 2 has a half-life that gets longer as the reaction proceeds.

You can suppose r = k [A]ⁿ, where n = 2 (second order reaction)Then, - d[A] / A² = k t1 / [A] = k t + 1 / [Ao]When you solve of t (half-life) you get: t (half-life) = = 1 / ( k [Ao] )This shows that for second order reactions, as the reaction proceeds ([Ao] decreases) the half-life increases.

When you do the same analysis for n > 2 (third or higher order reaction), you get the initial concenration raised to a power greater than two in the denominator, driving to the same conclusion, that as the reaction proceeds the half-life gets longer.

So, your second conclusion is that the seond reaction has an order greater than first.

Summarizing the two general conclusions:

the first reactions is a first order reaction. the second one should have an order greater than first.

That is the choice d. The first reaction is a first order reaction, the second one should have an order greater than first.