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uysha [10]
3 years ago
7

Suppose you were required to make a solution by diluting 20.0 mL of an aqueous solution to a final volume of 750 mL.

Chemistry
1 answer:
torisob [31]3 years ago
7 0
The first thing you do before performing anything in the laboratory is to read the procedure and prepare the materials needed. Next, if you already have the solution where you are supposed to take your 20 mL sample, then have it near you. Then, prepare a volumetric flask (750 mL) and a 20-mL pipette. Wash the pipette 3 times with the sample solution. If your diluent is water, wash the flask 3 times with water. Now, get 20 mL of sample from your parent solution, then add it to the flask (previously washed with water). Finally, add water until the mark in the flask and make sure that the water added is up to the mark based on the lower meniscus reading to be accurate in the amount inside the flask. <span />
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Compound C with molar mass 205gmol-1 , contains 3.758g of carbon , 0.316g of hydrogen and 1.251g of oxygen. Determine the molecu
labwork [276]

Answer:

Molecular formula => C₁₂H₁₂O₃

Explanation:

From the question given above, the following data were obtained:

Molar mass of compound = 205gmol¯¹

Mass of Carbon (C) = 3.758 g

Mass of Hydrogen (H) = 0.316 g

Mass of Oxygen (O) = 1.251 g

Molecular formula =?

We'll begin by determining the empirical formula of the compound. This can be obtained as follow:

C = 3.758 g

H = 0.316 g

O = 1.251 g

Divide by their molar masses

C = 3.758 /12 = 0.313

H = 0.316 /1 = 0.316

O = 1.251 /16 = 0.078

Divide by the smallest.

C = 0.313 / 0.078 = 4

H = 0.316 / 0.078 = 4

O = 0.078 / 0.078 = 1

Thus, the empirical formula of the compound is C₄H₄O

Finally, we shall determine the molecular formula of the compound. This can be obtained as follow:

Molar mass of compound = 205gmol¯¹

Empirical formula => C₄H₄O

Molecular formula =>?

[C₄H₄O]ₙ = 205

[(12×4) + (4×1) +16]n = 205

[48 + 4 +16]n = 205

68n = 205

Divide both side by n

n = 205 / 68

n = 3

Molecular formula => [C₄H₄O]ₙ

Molecular formula => [C₄H₄O]₃

Molecular formula => C₁₂H₁₂O₃

8 0
3 years ago
Calculate the molality for each of the following solutions. Then, calculate the freezing-point depression ΔTF = iKFcm produced b
zlopas [31]

Answer:

a) Cm= 3.9 m  ; ΔTf= 14.51 ºC

b) Cm= 0.21 m ; ΔTf= 0.79ºC

Explanation:

In order to solve the problems, we have to remember that the molality (m) of a solution is equal to moles of solute in 1 kg of solvent.

m= mol solute/kg solvent

a) In this case we have molarity, which is moles of solute in 1 liter of solution. We have to know how many kg of solvent (water) we have in 1 L of solution.

3.2 M NaCl= 3.2 mol NaCl/ 1 L solution

1 L solution= 1000 ml solution x 1.00 g/ml= 1000 g

A solution is composed by solute (NaCl) + solvent, so:

1000 g solution = g NaCl + g solvent

g NaCl= 3.2 mol NaCl x 58.44 g/mol= 187 g NaCl

g solvent= 1000 g - 187 g NaCl= 813 g= 0.813 kg

Cm= 3.2 g NaCl/0.813 kg solvent= 3.9 m

NaCl is an electrolyte and it dissociates in water in two ions: Na⁺ anc Cl⁻, si the van't Hoff factor (i) is 2.

ΔTf= i x KF x Cm= 2 x 1.86ºC/m x 3.9 m= 14.51ºC

b) In this case we have 24 g of solute in 1.5 L of solvent. We have to convert the liters of solvent to kg, and to convert the mass of solute to mol by using the molecular weight of KCl (74.55 g/mol):

24 g KCl x 1 mol KCl/74.55 g= 0.32 mol

1.5 L solvent= 1500 g solvent x 1.00 g/ml= 1500 g = 1.5 kg

Cm= 0.32 g KCl/1.5 kg solvent= 0.21 m

KCl is an electrolyte and when it dissolves in water, it dissociates in 2 ions: K⁺ and Cl⁻. For this, van't Hoff factor (i) is equal to 2.

ΔTf= i x KF x Cm= 2 x 1.86ºC x 0.21 m= 0.79ºC

7 0
3 years ago
Halppp can anyone come up with a slogan for anti smoking
PtichkaEL [24]

Answer:

"Your Choice: Liberation From Your Own Choices or Continue the Choice That Decreases Your Liberation."

Explanation:

Liberation is the freeing or release from something restraining you. In this case, smoking holds you back from doing the things you used to do.

It's not that creative, but I hope this is good enough for you! :D (don't smoke)

5 0
3 years ago
Mass x height x gravity is the formula to calculate:
Sindrei [870]

Answer:

Potential energy

Explanation:

p.e = mgh

8 0
3 years ago
Chemical bonds are likely to form when
shusha [124]
<span>b. an atom’s outer energy level doesn't have the maximum number of electrons.</span>
6 0
3 years ago
Read 2 more answers
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