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3 years ago

A 35.0 ml sample of 0.225 m hbr was titrated with 42.3 ml of koh. What is the concentration of the koh?

Chemistry

1 answer:

Lemur [1.5K]3 years ago

5 0

Answer:

The concentration of KOH is 0.186 M

Explanation:

First things first, we need too write out the balanced equation between HBr and KOH.

This is given as;

KOH (aq) + HBr (aq) → KBr (aq) + H2O (l)

From the reaction above, we can tell that it takes 1 mole of KOH to react with 1 mole of HBr.

We use the acid base formular in calculating unknown concentrations. This is given as;

$\frac{CaVa}{CbVb} = \frac{na}{nb}$

where;

Ca = Concentration of acid

Va = Volume of acid

Cb = Concentration of base

Vb = Volume of base

na = Number of moles of acid

nb = Number of moles of base

KOH is the base and HBr is acid.

Hence;

Ca = 0.225

Va = 35

Cb = ?

Vb = 42.3

na = 1

nb = 1

Making Cb subject of formular we have;

$Cb = \frac{CaVaNb}{VbNa}$

Cb = (0.225 * 35 * 1) / (42.3 * 1)

Cb = 0.186 M

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4 Al + 3O2 → 2Al2O3 If 14.6 grams Al are reacted, how many liters of O2 at STP would be required?

melomori [17]

Answer: 9.08 L

Explanation:

To calculate the moles :

$\text{Moles of solute}=\frac{\text{given mass}}\times{\text{Molar Mass}}$

$\text{Moles of} Al=\frac{14.6g}{27g/mol}=0.54moles$

$4Al+3O_2\rightarrow 2Al_2O_3$

According to stoichiometry :

4 moles of $Al$ require = 3 moles of $O_2$

Thus 0.54 moles of $Al$ will require= $\frac{3}{4}\times 0.54=0.405moles$ of $O_2$

Standard condition of temperature (STP) is 273 K and atmospheric pressure is 1 atm respectively.

According to the ideal gas equation:

$PV=nRT$

P = Pressure of the gas = 1 atm

V= Volume of the gas = ?

T= Temperature of the gas = 273 K

R= Gas constant = 0.0821 atmL/K mol

n= moles of gas= 0.405

$V=\frac{nRT}{P}=\frac{0.405\times 0.0821\times 273}{1}=9.08L$

Thus 9.08 L of $O_2$ at STP would be required

6 0

3 years ago

In a bottle of coke which would you expect to be higher, the concentration of H+ or the concentration of OH+? Why?

motikmotik

Answer: I don’t really know

Explanation:

I don’t know sorry

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3 years ago

Which of these statements about atomic models is most likely correct?

taurus [48]

Answer:

The correct option is the second option

Explanation:

Generally, the aim of science is to understand a particular concept in the best and the most correct way possible; hence experiments are done and repeated to ensure an explanation is actually true about a concept or need modification.

The atomic models have also been a "beneficiary" of this process. The different atomic models are usually been improved upon as scientists leaned more. For example, the Dalton's atomic theory has been modified to a more correct atomic description; some of which are shown below

(1) Dalton's theory suggested that an atom is the smallest unit of a molecule. We know now from different experiments (by J. J Thompson and Rutherford) that atoms are not the smallest molecules and are made up of smaller particles known as protons, neutrons and electrons.

(2) Dalton's theory suggested that atoms of the same elements are alike in all aspects. The knowledge of isotopy shows this is not always the case. As atoms of the same elements (isotopes) have the same atomic number but different mass number; hence cannot be said to be the same in all aspects.

(3) Dalton's theory also suggested that when atoms react, they do so in fixed, simple whole number ratio. The knowledge of organic chemistry shows atoms do not always react in simple whole number ratios

There are several modifications to different postulations by scientists that have also occurred aside from this, hence the most correct answer is that "As scientists learned more, they modified the atomic model"

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3 years ago

When atoms combine, the force of attraction that holds them together is a(

ziro4ka [17]

Electrostatic, meaning the attraction from one's positive nucleus is to the negative electrons of the other atom and vis versa.

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4 years ago

Consider the reaction pathway graph below.

igomit [66]

Answer:

subtract E from D

Explanation:

The graph shown the potential energy diagram of the reaction "reaction pathway".

X-axis represents the reaction progress, the transformation from the reactants to the products passing via the transition state.

Y-axis represents the potential energy of the reactants and the products and also the intermediate.

As clear from the attached image "F" represents the position of the reactants of the reaction, "B" represents the position of the intermediate/transition state and "G" represents the position of the products of the reaction.
Region "A" is the potential energy difference between the intermediate "B" and the reactants "F" which represents the activation energy of the reaction "Ea". Activation energy "Ea" can be defined as the minimum energy that the reactants should posses to initiate the reaction.
Region "C" is the potential energy difference between the reactants "F" and the products "G" which represents the enthalpy change of the reaction "ΔH".
<em>ΔH = pot. energy of the products "G" - pot. energy of the reactants "F".</em>
If "ΔH" is positive this means that the reaction is endothermic and this occurs when the potential energy of the products is greater than that of the reactants.

If "ΔH" is negative this means that the reaction is exothermic and this occurs when the potential energy of the products is smaller than that of the reactants.
In our example, It is obvious that the energy of the reactants is greater than the potential energy of the products.

So, ΔH will have a negative value which means that the reaction is exothermic reaction.
<em>Thus, the right choice is: "subtract E from D" would provide evidence to support the inference that this is an exothermic reaction.</em>

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3 years ago

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