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strojnjashka [21]
3 years ago
5

Explain how you would prepare a solution of sucrose with a molarity of 0.25.

Chemistry
1 answer:
Dimas [21]3 years ago
4 0
Solution of 0.25 M is prepared in two steps,

1) Calculate Amount of Solute:

                                Molar Mass of Solute:  342.3 g/mol

As we know,
                            Molarity  =  Moles / 1 dm³
or,
                            Moles     =  Molarity × 1 dm³
Putting Values,
                            Moles     =  0.25 mol.dm⁻³ × 1 dm³

                            Moles     =  0.25 moles

Now, find out mass of sucrose,
As,               
                            Moles      =   Mass / M.mass
or,
                            Mass       =  Moles × M.mass
Putting Values,
                            Mass       =  0.25 mol × 342.3 g.mol⁻¹

                            Mass       =  85.57 g

2) Prepare Solution:
                               Take Volumetric flask and add 85.57 g of sucrose in it. Then add distilled water up to the mark of 1 dm³. Shake well! The solution prepared is 0.25 M in 1 Liter.
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Give the half equation to show what happens to oxygen when it is rusting
ycow [4]

Answer:

½O 2 + 2e - + H 2O → 2OH.

Explanation:

Redox reactions - Higher

In terms of electrons:

oxidation is loss of electrons

reduction is gain of electrons

Rusting is a complex process. The example below show why both water and oxygen are needed for rusting to occur. They are interesting examples of oxidation, reduction and the use of half equations:

iron loses electrons and is oxidised to iron(II) ions: Fe → Fe2+ + 2e-

oxygen gains electrons in the presence of water and is reduced: ½O2 + 2e- + H2O → 2OH-

iron(II) ions lose electrons and are oxidised to iron(III) ions by oxygen: 2Fe2+ + ½O2 → 2Fe3+ + O2-

3 0
3 years ago
An iron bar of mass 841 g cools from 84°C to 7°C. Calculate the heat released (in kilojoules) by the metal.
Oduvanchick [21]

Answer:

28.75211 kj

Explanation:

Given data:

Mass of iron bar = 841 g

Initial temperature = 84°C

Final temperature = 7°C

Heat released = ?

Solution:

Specific heat capacity:

It is the amount of heat required to raise the temperature of one gram of substance by one degree.

specific heat capacity of iron is 0.444 j/g.°C

Formula:

Q = m.c. ΔT

Q = amount of heat absorbed or released

m = mass of given substance

c = specific heat capacity of substance

ΔT = change in temperature

ΔT = 7°C - 84°C

ΔT = -77°C

By putting values,

Q = 841 g × 0.444 j/g.°C × -77°C

Q = 28752.11 j

In Kj:

28752.11 j × 1 kJ / 1000 J

28.75211 kj

8 0
3 years ago
Help please the questions are confusing
SashulF [63]

Answer:

5- number of electrons=11

Explanation:

in a neutral atom number of protons=number of electrons which in this case=11

3 0
4 years ago
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What is the relationship between the degree of ionization and conductivity
LuckyWell [14K]
The higher the degree of ionization, the stronger the conductivity
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A major component of gasoline is octane. When liquid octane is burned in air it reacts with oxygen gas to produce carbon dioxide
irakobra [83]

Answer:

0.267 mol

Explanation:

The <em>unbalanced equation</em> for the reaction that takes place is:

  • C₈H₁₈ + O₂ → H₂O + CO₂

Once we balance it we're left with:

  • 2C₈H₁₈ + 25O₂ → 18H₂O + 16CO₂

Using the <em>stoichiometric ratio </em>of water and octane from the balanced reaction, we can <u>convert mol of water into mol of octane</u>:

  • 2.40 mol H₂O * \frac{2molC_8H_{18}}{18molH_2O} = 0.267 mol C₈H₁₈

Thus 0.267 moles of octane are needed to produce 2.40 mol of water.

5 0
3 years ago
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