CHEMISTRY HIGH SCHOOL

In which laboratory process could a student use 0.10 M NaOH(aq) to determine the concentration of an aqueous solution of HBr?(1) chromatography
(2) decomposition of the solute
(3) evaporation of the solvent
(4) titration

Answers

Answer 1
Answer:

Answer:

4) titration

Explanation:

Titration is a standard process used in a laboratory to determine the concentration of an unknown analyte. A titrant of known concentration is gradually added to a known volume of the analyte in the presence of a suitable indicator. The end of the titration is marked by a color change of the analyte.

The given example is that of an acid(HBr) - base(NaOH) titration which can be represented by the following equation:

NaOH + HBr → NaBr + H2O

Thus  1 mole of acid gets neutralized by 1 mole of the base to form 1 mole of the salt (NaBr)

Let M1 and V1 are the molarity and volume of the base (NaOH). Here, the molarity of NaOH is known = M1 =  0.10 M and the volume, V1 corresponds to the end point in the titration.

M2 and V2 are the molarity and volume of HBr. Here, V2 is  known whereas M2 needs to be determined.

Based on the reaction stoichiometry:

moles of NaOH = moles of HBr

M1*V1=M2*V2\n\nTherefore,\n\nM2 = (M1*V1)/(V2)
Answer 2
Answer: (4) titration, the process of using an aqueous solution of known concentration to determine the concentration of another solution of unknown concentration, is your answer.

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The mass and volume of each sample differ from the mass and volume of the other samples. Is it possible for each sample to contain 1 mol of each substance?No, because they have different masses.
No, because they have different volumes.
Yes, because the number of moles is not dependent on the mass or the volume.
Yes, because the number of moles is only dependent on the mass per unit volume.

Answers

Answer: Yes, it is possible for each samples to contain 1 mole of a substance because the number of moles are not dependent on the mass or the volume.

Explanation:

The formula for the number of moles is given by:

\text{number of moles}=\frac{\text{given mass}}{\text{molar mass}}

As, the masses of 2 samples are different, so the number of moles will be dependent only on the molar masses of the samples.

Volume has no effect on the number of moles.
Yes, because the number of moles is not dependent on the mass or the volume.
Different elements and compounds have different molar masses. E.g. a mole of hydrogen would be very different from a mole of gold

What is the ph at the equivalence point when 0.10 m hno3 is used to titrate a volume of solution containing 0.30 g of koh?

Answers

Answer;

pH = 7  

Explanation;

  • HNO3 is a strong acid. KOH is a strong base. At the equivalence point, the solution will be neutral.
  • Therefore; the pH at the equivalence point when 0.10 m HNO3 is used to titrate a volume of solution containing 0.30 g of KOH will be 7.
  • The neutralization of a strong base with a strong acid gives a salt solution at the equivalence point. The salt contains ions that do not change the pH of water.

Answer:

pH at equivalence point will be 7

Explanation:

  • HNO_(3) is a strong acid and KOH is a strong base. Hence a neutral salt would appear from acid-base reaction between them.
  • Acid-base reaction: HNO_(3)+KOH\rightarrow KNO_(3)+H_(2)O
  • At equivalence point, KNO_(3) and water exists in medium.
  • As KNO_(3) is a neutral salt therefore pH of medium will be equal to 7 (neutral).
  • So, pH at equivalence point will be 7.

Which condensed structural formula represents an unsaturated compound?(1) CH3CHCHCH3
(2) CH3CH2CH3
(3) CH3CH3
(4) CH4

Answers

Answer: The correct answer is option (1).

Explanation:

The general formula of alkanes (Saturated compounds) is given as:C_nH_(2n+2)

The general formula of alkene  (Unsaturated compounds)is given as:C_nH_(2n)

The general formula of alkynes (Unsaturated compounds)is given as:C_nH_(2n-2)

1. CH_3CHCHCH_3:C_4H_8 unsaturated hydrocarbon

2. CH_3CH_2CH_3:C_3H_8 Saturated hydrocarbon

3.CH_3CH_3:C_2H_6 Saturate hydrocarbon

4. CH_4 Saturated hydrocarbon
Number(1).A carbon atom makes 4 bondings.As the second Carbon in the conpuond has only one hidrogen,it has to make other 3,two with the other carbon atoms,one of them Being a double,making the compound unsaturated.PS:Sorry for my english,um fron Brazil

Choose the pieces of evidence that supported the existence of Pangaea and continental drift theory.o Fossilized plants and animals of the same species found on separate continents.
o Geological features, such as mountain ranges, that align on matching coasts of different continents.
o Island arc ranges are still connected under the Atlantic Ocean.
o Antarctica's glacial features are similar to the Arctic's.

Answers

Pangaea is scientifically known as the original whole mass of land that eventually was divided into separate mass entities called continents as a result to natural phenomena like earthquakes. This is more explained inthe continental drift theory. After rigorous collection of evidences, scientists noticed that fossilized plants and animals of the same species, also with the coastlines match on different continents. The answers are the first and second choices (A and B).

Fossilized plants and animals of the same species found on separate continents.

Geological features, such as mountain ranges, that align on matching coasts of different continents.

The radius of an atom of gold (Au) is about 1.35 Å.How many gold atoms would have to be lined up to span 9.5 mm ?

Answers

Answer : The number of gold atoms will be, 3.52* 10^7

Explanation :

First we have to determine the diameter of an atom of gold.

Diameter=2* Radius

Given :

Radius of an atom of gold = 1.35\AA

Diameter=2* 1.35\AA=2.7\AA

Conversion used :(1\AA=10^(-7)mm)

Diameter=2.7\AA=2.7* 10^(-7)mm

Now we have to calculate the number of gold atoms.

\text{Number of gold atoms}=\frac{\text{Span length}}{\text{Diameter of an atom of gold}}

\text{Number of gold atoms}=(9.5mm)/(2.7* 10^(-7)mm)=3.52* 10^7

Therefore, the number of gold atoms will be 3.52* 10^7
Two radius of an atom is equal to the diameter. Adding up all the diameter of  the atoms, it should be equal to 9.5 mm. Therefore, we simply convert the units to the same units then divide 1.35 A to 9.5 mm. We calculate as follows:

no. of atoms = 0.0095 m / 1.35x10^-9 m = 7037037 atoms 

Hope this answers the question. Have a nice day.

I need help with this molecular formula problem really quick!!

Answers

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Explanation: The empirical formula is the most reduced whole number ratio of elements. N2O4 is the only compound that can be further reduced, making the empirical formula NO2, and thus is different from the molecular formula.
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