Chemistry, 19.07.2019 10:00 pinkycupcakes3oxbqhx

How many grams of na2s do we need to dissolve in 200ml of water to get a solution that is 0.2 m?

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We know that the molarity of a solution is calculated by the following equation:

$Molarity = \frac{# moles}{L}$

That being said we are given two of the 3 things that we need: Volume of water, as well as the molarity of the solution. Let's plug those in to the equation to find how many moles of $Na_{2}S$ that we need:

$0.2 M = \frac{moles}{0.2 L}$ => moles =0.04

This means that we have 0.04 moles of $Na_{2}S$ .

In order to calculate the number of grams that we need for this solution, we must first calculate how many grams of $Na_{2}S$ are in 1 mole. We do this by taking the atomic masses of each element from the periodic table and adding them together.

Na = 22.99 g
S = 32.06 g

We have 2 Na's, and we have 1 S. So lets add them together:

2(22.99) + (32.06) = $\frac{78.04g}{mol}$ .

Since we need 0.04 moles of $Na_{2}S$ , we can multiply the molar weight of the molecule times the amount of moles needed to find the total grams that we need for the solution:

$\frac{78.04g}{mol}*0.04 moles = 3.1216 g$

Now we know that in order to make a 0.2 M solution of $Na_{2}S$ , we must use 3.1216 grams.

Answer from: Quest

if the concentration of products is decreased, the equilibrium will shift toward the products). add an inert gas (one that is not involved in the reaction) to the constant-volume reaction mixture: this will increase the total pressure of the system, but will have no effect on the equilibrium condition.

explanation:

Answer from: Quest

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence, the electronegativity (or the ability to attract electrons) is lessened."

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