Answer:
28.58 g of NaOH
Explanation:
The question is incomplete. The missing part is:
<em>"Calculate the mass of sodium hydroxide that the chemist must weigh out in the second step"</em>
To do this, we need to know how much of the base we have to weight to prepare this solution.
First we know that is a sodium hydroxide aqueous solution so, this will dissociate in the ions:
NaOH -------> Na⁺ + OH⁻
As NaOH is a strong base, it will dissociate completely in solution, so, starting with the pH we need to calculate the concentration of OH⁻.
This can be done with the following expression:
14 = pH + pOH
and pOH = -log[OH⁻]
So all we have to do is solve for pOH and then, [OH⁻]. To get the pOH:
pOH = 14 - 13.9 = 0.10
[OH⁻] = 10⁽⁻⁰°¹⁰⁾
[OH⁻] = 0.794 M
Now that we have the concentration, let's calculate the moles that needs to be in the 900 mL:
n = M * V
n = 0.794 * 0.9
n = 0.7146 moles
Finally, to get the mass that need to be weighted, we need to molecular mass of NaOH which is 39.997 g/mol so the mass:
m = 39.997 * 0.7146
<h2>
m = 28.58 g</h2>
Answer:
D. Na₂SO₃
Explanation:
The given equation is:
2HNO₃ + Na₂SO₃ → 2NaNO₃ + H₂O + SO₂
The reaction equation is shown above. In chemical reactions, the left hand side is made up of the reactants and the right hand side is made up of the products.
The reactants in the equation are:
HNO₃ and Na₂SO₃
Answer:
Distance, direction and symbol.
Explanation:
Distance, direction and symbol are the three components of the map which make a complete description of a location. On the map, these three components are present which provides information about a specific location on the map. Map is a drawing on the paper that shows the geography of the whole world and provides information in detail.
Answer : The chemical symbol for this element is, (La)
Explanation : Given,
Mass of
= 0.760 g
Mass of
= 1.610 g
The given chemical reaction is:

First we have to calculate the moles of
and
.

Molar mass of Cl = 35.5 g/mole
Let the molar mass of element 'X' be, M
![\text{Moles of }XCl_3=\frac{0.760}{[M+3(35.5)]}](https://tex.z-dn.net/?f=%5Ctext%7BMoles%20of%20%7DXCl_3%3D%5Cfrac%7B0.760%7D%7B%5BM%2B3%2835.5%29%5D%7D)
and,

Molar mass of I = 126.9 g/mole
Let the molar mass of element 'X' be, M
![\text{Moles of }XI_3=\frac{1.610}{[M+3(126.9)]}](https://tex.z-dn.net/?f=%5Ctext%7BMoles%20of%20%7DXI_3%3D%5Cfrac%7B1.610%7D%7B%5BM%2B3%28126.9%29%5D%7D)
From the balanced chemical reaction we conclude that,
The moles of ratio of
and
is, 1 : 1
That means,
![\frac{0.760}{[M+3(35.5)]}=\frac{1.610}{[M+3(126.9)]}](https://tex.z-dn.net/?f=%5Cfrac%7B0.760%7D%7B%5BM%2B3%2835.5%29%5D%7D%3D%5Cfrac%7B1.610%7D%7B%5BM%2B3%28126.9%29%5D%7D)
![\frac{0.760}{[M+106.5]}=\frac{1.610}{[M+380.7]}](https://tex.z-dn.net/?f=%5Cfrac%7B0.760%7D%7B%5BM%2B106.5%5D%7D%3D%5Cfrac%7B1.610%7D%7B%5BM%2B380.7%5D%7D)

From this we conclude that the element (X) is lanthanum (La) that has molecular weight, 138.667 g/mol.
Hence, the chemical symbol for this element is, (La)
Answer:

Explanation:
Given that:

From equation (3) , multiplying (-1) with equation (3) and interchanging reactant with the product side; we have:

Multiplying (2) with equation (4) ; we have:

From equation (1) ; multiplying (-1) with equation (1); we have:

From equation (2); multiplying (3) with equation (2); we have:

Now; Adding up equation (5), (6) & (7) ; we get:



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(According to Hess Law)

