Chemistry High School

What is the concentration (in molality) of an aqueous solution of NaCl made by adding
4.56 g of NaCl to enough water to give 20.0 mL of solution. Assume the density of the
solution is 1.03 g/mL

Answers

Answer 1

Answer:

data given

mass of NaCl 4.56

dissolved volume 20ml(0.02l)

density of solution 1.03g/ml

Required molality

Explanation:

molarity=m/mr×v

where

m is mass

mr molar mass

v is volume

now,

molarity=4.56/58.5×0.02

molarity =3.9

: .molarity is 3.9mol/dm^3

Answer 2

According to molal concentration, the concentration (in molality) of an aqueous solution of NaCl is 0.0047 mole/kg.

What is molal concentration?

Molal concentration is defined as a measure by which concentration of chemical substances present in a solution are determined. It is defined in particular reference to solute concentration in a solution . Most commonly used unit for molal concentration is moles/kg.

The molal concentration depends on change in volume of the solution which is mainly due to thermal expansion. Molal concentration is calculated by the formula, molal concentration=mass/ molar mass ×1/mass of solvent in kg.

In terms of moles, it's formula is given as molal concentration= number of moles /mass of solvent in kg.

Substitution in formula gives the answer but first mass of solution is determined which  is density×volume= 1.03×20=20.6 g , mass of solvent= 20.6-4.56=16.05, thus molal concentration=4.56/58.5×1/16.05=0.0047 moles/kg.

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Related Questions

a 1.25 g sample of co2 is contained in a 750. ml flask at 22.5 c. what is the pressure of the gas, in atm?

Answers

The pressure of gas is 1.05 atm when a 1.25 g sample of CO₂ is contained in a 750ml flask at 22.5°C.

Molecular weight of CO₂ is 1.25g ,Volume of CO₂ is 750ml,Temperature of CO₂ is 22.5°C and the gas constant is 0.08206 L atm/mol K.

Using the ideal gas law equation the pressure is found to be 1.05 atm.

To calculate the pressure of the gas, we can use the ideal gas law equation: [tex]PV=nRT[/tex]
Where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature in Kelvin.
First, we need to convert the volume to liters by dividing by 1000: 750 ml = 0.75 L.
Next, we need to calculate the number of moles of CO₂ present in the flask. We can use the molecular weight of CO₂ to convert from grams to moles:

[tex]1.25 * (1 /44.01 ) = 0.0284 mol[/tex]
Now we can plug in the values into the ideal gas law equation:

[tex]PV=nRT[/tex]
[tex]P * 0.75 L = 0.0284 mol  * 0.08206 L*atm/mol*K * (22.5 + 273.15) K[/tex]
Simplifying and solving for P, we get:
[tex]P = (0.0284 * 0.08206 * 295.65) / 0.75 = 1.05 atm[/tex]
Therefore, the pressure of the gas in the flask is 1.05 atm.

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you have 400 grams (g) of a substance with a half life of 10 years. how much is left after 100 years?

Answers

After 100 years, there will be 6.25 grams of the substance remaining.

What is half life?

Half-life is the time it takes for half of the radioactive atoms in a sample to decay or for the concentration of a substance to decrease by half.

Amount remaining = initial amount x (1/2)^(number of half-lives)

In this case,  half-life of the substance is 10 years, which means that after 10 years, half of the substance will have decayed. After another 10 years (20 years total), half of remaining substance will decay, leaving 1/4 of the original amount. After another 10 years (30 years total), half of that remaining amount will decay, leaving 1/8 of the original amount. This process continues every 10 years.

To find the amount of substance remaining after 100 years, we need to know how many half-lives have occurred in that time: 100 years / 10 years per half-life = 10 half-lives

Amount remaining = 400 g x (1/2)¹⁰= 6.25 g

Therefore, after 100 years, there will be 6.25 grams of the substance remaining.

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which of the following is true about the absorption and metabolism of alcohol? alcohol is metabolized by most tissue and organs in the body. the majority of alcohol is absorbed in the stomach. men and women do not metabolize alcohol at significantly different rates. acetaldehyde produced during alcohol metabolism is highly toxic.

Answers

The statement "acetaldehyde produced during alcohol metabolism is highly toxic" is true about absorption and metabolism of alcohol. Option 4 is correct.

Acetaldehyde is a byproduct of alcohol metabolism, and it is a toxic substance that can cause various symptoms such as facial flushing, nausea, and headache. Acetaldehyde is rapidly converted to acetate by the enzyme aldehyde dehydrogenase, which is then metabolized further to carbon dioxide and water.

However, if alcohol is consumed at a high rate, the liver may not be able to metabolize all of the acetaldehyde, leading to a buildup of this toxic substance in the body. This can result in more severe symptoms such as vomiting, rapid heartbeat, and difficulty breathing. Therefore, it is important to consume alcohol in moderation and allow enough time for the liver to metabolize the alcohol and its byproducts. Hence Option 4 is correct.

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addictive substances, for which demand is inelastic, are products for which producers can pass higher costs on to consumers.

Answers

The statement is correct. Producers of addictive substances, for which demand is inelastic, can pass higher costs on to consumers.

Inelastic demand refers to a situation where changes in price have little effect on the quantity demanded of a product. Addictive substances, such as tobacco or drugs, often have inelastic demand because users are willing to pay high prices for the product regardless of changes in price.

Producers of addictive substances can take advantage of this inelastic demand by increasing prices without seeing a significant decrease in demand. This means that they can pass on any higher costs, such as increased taxes or production costs, to the consumers, who are likely to continue purchasing the product even at a higher price.

This is often seen in the tobacco industry, where governments may increase taxes on cigarettes as a way to discourage smoking, but the tobacco companies can simply pass on the higher costs to consumers who continue to buy the product.

Therefore, it can be concluded that producers of addictive substances, for which demand is inelastic, can pass higher costs on to consumers.

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