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2 years ago

A chemist needs 0.550 mol selenium for a reaction. What mass of selenium should a chemist use?

Chemistry

1 answer:

-BARSIC- [3]2 years ago

4 0

Answer:

The chemist would require to use 43.43 grams.

Explanation:

In order to solve this problem we need to know how much do 0.550 moles of selenium weigh. To do that we use selenium's molar mass and multiply it by the given number of moles:

0.550 mol * 78.96 g/mol = 43.43 g

The chemist would require to use 43.43 grams.

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A 33.0 mL sample of 1.15 M KBr and a 59.0 mL sample of 0.660 M KBr are mixed. The solution is then heated to evaporate water unt

Oksi-84 [34.3K]

Answer:

We need 13.06 grams of silver nitrate to precipitate out silver bromide in the final solution

Explanation:

Step 1: Data given

Sample 1: The 1.15 M sample has a volume of 33.O mL

Sample 2: The 0.660 M sample has a volume of 59.0 mL

Molar mass of KBr = 119 g/mol

Molar mass of AgNO3 = 169.87 g/mol

Step 2: Calculate number of moles for both samples

Number of moles = Molarity * Volume

Sample 1: 1.15 M * 33 *10^-3 L = 0.03795 moles

Sample 2: 0.660 M *59*10^-3 L = 0.03894 moles

Total mol KBr = 0.03795 + 0.03894 = 0.07689 moles

Step 3: Calculate total mass

mass = Number of moles * Molar mass

mass = 0.07689 moles * 119 g/moles = 9.15 grams ( in 55mL)

Step 4: Calculate moles of AgBr

AgNO3 reacts with KBr

KBr(aq) + AgNO3(aq) → AgBr(s) + KNO3(aq)

1 mole of KBr consumed, needs 1 mole of AgNO3 to produce 1 mole of AgBr and 1 mole of KNO3

So 0.07689 moles of KBr wll need 0.07689 moles of AgNO3

Step 5: Calculate mass of silver nitrate

mass of AgNO3 = Moles of AgNO3 * Molar mass of AgNO3

mass of AgNO3 = 0.07689 moles * 169.87 g/mol = 13.06 grams

We need 13.06 grams of silver nitrate to precipitate out silver bromide in the final solution

8 0

3 years ago

Which of the followings is true about G0'? A. G0' can be determined using Keq' B. G0' indicates if a reaction can occur under no

nekit [7.7K]

Answer:

A and D are true , while B and F statements are false.

Explanation:

A) True. Since the standard gibbs free energy is

ΔG = ΔG⁰ + RT*ln Q

where Q= [P1]ᵃ.../([R1]ᵇ...) , representing the ratio of the product of concentration of chemical reaction products P and the product of concentration of chemical reaction reactants R

when the system reaches equilibrium ΔG=0 and Q=Keq

0 = ΔG⁰ + RT*ln Q → ΔG⁰ = (-RT*ln Keq)

therefore the first equation also can be expressed as

ΔG = RT*ln (Q/Keq)

thus the standard gibbs free energy can be determined using Keq

B) False. ΔG⁰ represents the change of free energy under standard conditions . Nevertheless , it will give us a clue about the ΔG around the standard conditions .For example if ΔG⁰>>0 then is likely that ΔG>0 ( from the first equation) if the temperature or concentration changes are not very distant from the standard conditions

C) False. From the equation presented

ΔG⁰ = (-RT*ln Keq)

ΔG⁰>0 if Keq<1 and ΔG⁰<0 if Keq>1

for example, for a reversible reaction ΔG⁰ will be <0 for forward or reverse reaction and the ΔG⁰ will be >0 for the other one ( reverse or forward reaction)

D) True. Standard conditions refer to

T= 298 K

pH= 7

P= 1 atm

C= 1 M for all reactants

Water = 55.6 M

5 0

2 years ago

What is a coefficient?

mario62 [17]

Answer:

Coefficients are the numbers in front of the formulas.

4 0

3 years ago

Read 2 more answers

Which two statements describe what happens to the nuclei of atoms during a fusion reaction? O A. Large nuclei break apart into t

pashok25 [27]

Answer:

D. Nuclei with small masses combine to form nuclei with larger masses.

B. A small amount of mass in the nuclei that combine is converted to energy

Explanation:

A nuclear fusion, in contrary to fission, is the process by which the nuclei of two atoms combine to form a much larger atom with a large nuclei. Likewise, during a fusion reaction, a large amount of energy is released from the small amount of mass in the nuclei (two) that combines.

According to this question, the following are true of a fusion reaction:

- Nuclei with small masses combine to form nuclei with larger masses.

- A small amount of mass in the nuclei that combine is converted to enormous energy.

3 0

2 years ago

Read 2 more answers

Ionic or covalent C2H5OH

Afina-wow [57]

Answer:

Covalent

Explanation:

A molecule of C₂H₅OH has C-C, C-H, C-O, and O-H bonds.

A bond between A and B will be ionic if the difference between their electronegativities (ΔEN) is greater than 1.6.

$\begin{array}{ccc}\textbf{Bond} & \textbf{$\Delta$EN} & \textbf{Polarity}\\\text{C-C} & 2.55 - 2.55 = 0.00 & \text{Nonpolar covalent}\\\text{C-H} & 2.55 - 2.20 = 0.35 & \text{Nonpolar covalent}\\\text{C-O} & 3.44 - 2.55 = 0.89 & \text{Polar covalent}\\\text{O-H} & 3.44 - 2.20 = 1.24 & \text{Polar covalent}\\\end{array}$

No bond has a large enough ΔEN to be ionic.

C₂H₅OH is a covalent molecule.

6 0

2 years ago