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3 years ago

A solution with the concentration of 0.15 M is made using 8.00 grams of K2CrO4. How many milliliters of H2O should be used?

Chemistry

1 answer:

babymother [125]3 years ago

6 0

Answer:

274.7mL

Explanation:

Molarity is defined as the number of mols of solute per liter of the solvent. Here, the solute is potassium chromate ( $K_{2}CrO_{4}$ ) and the solvent is water. Hence, molarity is defined as the number of mols of potassium chromate per litre of water. And this molarity is equal to 0.15M.

Now, the molar mass of potassium chromate can be found by simply adding the atomic masses of the component atoms. This is equal to : 2×atomic mass of potassium + 1×atomic mass of chromium + 4×atomic mass of oxygen = 2×39 + 52 + 4×16 = 194g /mol.

The number of mols of potassium chromate is the ratio of the given mass of potassium chromate to the molar mass of potassium chromate.

Here, this is equal to $\frac{8}{194}$ = 0.0412 mols.

This much potassium chromate is present in 'V' litres of water. Hence, molarity is given by : 0.15 = $\frac{0.0412}{V}$ .

Thus, V = $\frac{0.0412}{0.15}$ = 0.2747L = 274.7mL

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what is the volume of a sample of liquid mercury that has a mass of 76.2 g, given that the density of mercury is 13.6 g/ml?

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24 square root . i know im wrong but so what

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3 years ago

Using the standard reduction potentials, Pb 2+(aq) + 2e– => Pb(s), E° = –0.13 V Fe 2+(aq) + 2e– => Fe(s), E° = –0.44 V Zn

mojhsa [17]

Answer:

Pb(s), Fe(s) and Zn(s) will reduce $Mn^{3+}$ to $Mn^{2+}$

Fe(s) and Zn(s) will reduce $Cr^{3+}$ to $Cr$

Explanation:

Standard reduction potential denotes ability to consume electrons from another species.

Hence, higher the standard reduction potential, higher will be the ability to oxidize another species.

Metal with $E_{red}^{0}$ value lower than 1.51 V will donate electron to $Mn^{3+}$ and thus reduces $Mn^{3+}$ to $Mn^{2+}$ .

So, Pb(s), Fe(s) and Zn(s) will reduce $Mn^{3+}$ to $Mn^{2+}$ .

Metal with $E_{red}^{0}$ value lower than -0.40 V will donate electron to $Cr^{3+}$ and thus reduces $Cr^{3+}$ to $Cr$ .

So, Fe(s) and Zn(s) will reduce $Cr^{3+}$ to $Cr$ .

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3 years ago

Who is allowed to go into a crime scene after its released?

Gala2k [10]

Answer:

detectives, police officers and occasionaly lawyers/attorneys.

Explanation:

Non essential officers, judges, district attorney investigators, federal agents, victums, witnesses and politics are not permited to enter crime scenes unless they can provide information and history about the event.

6 0

3 years ago

Hydrocyanic acid, HCN, is a weak acid. (a) Write the chemical equation for the dissociation of HCN in water. (b) Identify the Br

12345 [234]

Answer: a) $HCN(aq.)+H_2O\rightleftharoons H_3O^+(aq.)+CN^-(aq.)$

b) $HCN$ : acid $CN^-$ :conjugate base.

And, $H_2O$ : base $H_3O^+$ : conjugate acid.

c) $HCN(aq.)+NaOH(aq)\rightleftharoons NaCN(aq.)+H_2O(l)$

d) $NaCN(aq)\rightarrow Na^+(aq.)+CN^-(aq)$

e) $NaCN(aq)+HCl(aq)\rightarrow NaCl(aq.)+HCN(aq)$

Explanation:

a) Weak acid is defined as the acid which does not completely dissociates when dissolved in water. They have high pH. These releases $H^+$ ions in their aqueous states.

The equation for the dissociation of $HCN$ acid is given by:

$HCN(aq.)+H_2O\rightleftharoons H_3O^+(aq.)+CN^-(aq.)$

b) According to the Bronsted-Lowry conjugate acid-base theory, an acid is defined as a substance which looses donates protons and thus forming conjugate base and a base is defined as a substance which accepts protons and thus forming conjugate acid.

For the given chemical equation:

$HCN$ is loosing a proton, thus it is considered as an acid and after losing a proton, it forms $CN^-$ which is a conjugate base.

And, $H_2O$ is gaining a proton, thus it is considered as a base and after gaining a proton, it forms $H_3O^+$ which is a conjugate acid.

c) Neutralization reaction is a reaction in which an acid reacts with base to produce salt and water.

$HCN(aq.)+NaOH(aq)\rightarrow NaCN(aq.)+H_2O(l)$

d) The chemical equation for dissociation of $NaCN$ in water.

$NaCN(aq)\rightarrow Na^+(aq.)+CN^-(aq)$

e) The chemical equation for the reaction of $NaCN$ and $HCI$

$NaCN(aq)+HCl(aq)\rightarrow NaCl(aq.)+HCN(aq)$

4 0

3 years ago

Suppose 'A' is a liquid aromatic compound with molecular weight 78 and burns with sooty flame. a.Give the name of the compound '

Oliga [24]

Aromatic compounds are compounds that contain carbon-carbon multiple bonds.

The question did not mention that a heteroatom is present in the compound so we can assume that there is none of such. In that case, the compound contains only hydrogen and carbon.

So,

(CH)n = 78

where n is the number of each atom present.

(12 +1)n = 78

n = 78/13

n = 6

The molecular formula of the compound is C6H6

When C6H6 is treated with .conc.HNO3/conc.H2SO4 the compound shown in image 1 is formed. The reaction occurs at the C-C multiple bond.

When C6H6 is reacted with chlorine in the presence of sunlight, hexachlorobenzene (shown in image 2 attached) is formed.

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