Hey there!
Stock solution:
Concentracion bromide = 0.128 M
initial solution in volumetric flask = 450 µl
So , moles of bromide present:
450 µl in liters :
1 µl = = 1*10⁻⁶ liters
450 * ( 1*10⁻⁶ ) = 0.00045
0.128 * 0.00045 => 57.6 * 10⁻⁶ moles
Now volume final is 25 mL , in liters : 0.025 L ou 25*10⁻³
so new bromide concentration:
57.6*10⁻⁶ / 25*10⁻³=> 2.304*10⁻³ M
The original concentration of the acid solution is 6.175 10^-4 mol / L.
<u>Explanation:</u>
Concentration is the ratio of solute in a solution to either solvent or total solution. It is expressed in terms of mass per unit volume
HBr + NaOH -----> NaBr + H2O
There is a 1:1 equivalence with acid and base.
Moles of NaOH = 72.90 10^-3 0.25
= 0.0182 mol.
[ HBr ] = moles of base / volume of a solution
= 0.0182 / 29.47
= 6.175 10^-4 mol / L.
Answer: The correct option is:
Explanation:
In balanced chemical equation , mass of the reactants is always equal to the mass of the products.
This is the balanced equation because on both sides number of sodium and bromine atoms are same.
On the reactant side there are two sodium atoms and two bromine atoms
On the product side there are also two sodium atoms and two bromine atoms in NaBr.
Mass of reactants (here 2Na and )= Mass of products(here 2NaBr)
2(23u) + 2(79.9u) = 2(23u + 79.9u) = 205 u
The reactants are the substances on the left side, which react and give the products on the right side.
The reactants are Fe and O.
The product is Fe2O3.
The arrow to the right means that the reaction is going in only one direction — the only reaction happening at the moment is that Fe and O are making Fe2O3.
(s) means the substance is in the solid state, and (g) means in a gaseous state (or the substance is a gas in that reaction).