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2 years ago

What's the molality of a solution with 120 g of NaCl and 30 kg of water?

Chemistry

1 answer:

pogonyaev2 years ago

4 0

Answer: The correct option is A) 0.068 m

Explanation:

Molality is defined as the amount of solute expressed in the number of moles present per kilogram of solvent. The units of molarity are mol/kg. The formula used to calculate molarity:

$\text{Molality of solution}=\frac{\text{Given mass of solute}}{\text{Molar mass of solute}\times \text{Mass of solvent (in kg)}}$ .....(1)

We are given:

Given mass of NaCl = 120 g

Molar mass of NaCl = 58.45 g/mol

Mass of solvent = 30 kg

Putting values in equation 1, we get:

$\text{Molality of NaCl}=\frac{120}{58.44\times 30}\\\\\text{Molality of NaCl}=0.068m$

Hence, the correct option is A) 0.068 m

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1. A substance, A₂B, has the composition by mass of 60% A and 40% B. What is the composition of AB₂ by mass?

Lubov Fominskaja [6]

This may help you
Use an arbitrary mass, 100 g is an easy number to work with. 60% of 100 g is 60 g, there are two A's. Each A is 30 g 40 g is B, and there is only one, so B is 40 g. AB2, would have a mass of 30 g + 2*40 g = 110 g The new percent by mass composition of A is: 30g110g∗100%=27.3% The new percent by mass composition of B is: 80g110g∗100%=72.7%

8 0

3 years ago

A 45-g aluminium spoon(specific heat 0.80 / J/gdegree Celsius) at 24 degree celsius is placed in 180 ml(180 grams) of coffee at

Vlad [161]

Explanation:

a) The amount of heat released by coffee will be absorbed by aluminium spoon.

Thus, $heat_{absorbed}=heat_{released}$

To calculate the amount of heat released or absorbed, we use the equation:

$Q=m\times c\times \Delta T=m\times c\times (T_{final}-T_{initial})$

Also,

$m_1\times c_1\times (T_{final}-T_1)=-[m_2\times c_2\times (T_{final}-T_2)]$ ..........(1)

where,

q = heat absorbed or released

$m_1$ = mass of aluminium = 45 g

$m_2$ = mass of coffee = 180 g

$T_{final}$ = final temperature = ?

$T_1$ = temperature of aluminium = $24^oC$

$T_2$ = temperature of coffee = $85^oC$

$c_1$ = specific heat of aluminium = $0.80J/g^oC$

$c_2$ = specific heat of coffee= $4.186 J/g^oC$

Putting all the values in equation 1, we get:

$45 g\times 0.80J/g^oC\times (T_{final}-24^oC)=-[180 g\times 4.186J/g^oC\times (T_{final}-83^oC)]$

$T_{final}=80.30^oC$

80.30 °C is the final temperature.

b) Energy flows from higher temperature to lower temperature.Whenever two bodies with different energies and temperature come in contact. And the resulting temperature of both bodies will less then the body with high temperature and will be more then the body with lower temperature.

So, is our final temperature of both aluminium and coffee that is 80°C less than initial temperature of coffee and more than the initial temperature of the aluminum.

8 0

2 years ago

This figure (Figure 1)shows a container that is sealed at the top

guajiro [1.7K]

I'm pretty sure the answer is 0.833 atm.

Hope I helped! <3

-cara

7 0

3 years ago

A chemist mixes sodium with water and witnesses a violent reaction between the metal and water. this is best classified as

Tema [17]

A law is statement about an observed concept. A theory involves the explanation of scientific concepts or principles. A hypothesis is the predicted explanation about some concepts that has to be tested in order to prove it to be right. An observation is the observing the results of a scientific experiment carried out to test an hypothesis.

Here the given statement 'A chemist mixes sodium with water and witnesses a violent reaction between the metal and water,' can be classified as an observation as it explains what the chemists observes as a result of his chemical experiment or test..

8 0

3 years ago

Identify the oxidation state of Ba 2 + . +2 Identify the oxidation state of S in SO 2 . +2 Identify the oxidation state of S in

cupoosta [38]

Answer:

The oxidation state of Ba in cation Ba²⁺ is +2

The oxidation state of S in SO₂, is +4

The oxidation state of S in anion sulfate (SO₄⁻²) is +6

The oxidation state of Zn in the Zinc sulfate, is +2

Explanation:

We define oxidation state as the number which can be negative or positive that

indicates the number of electrons that the atom has accepted or transferred.

All the elements in ground state has 0 as oxidation state.

This numbers are very important for redox reaction which are balanced by the ion electron method.

When the elements gain electrons, the element is being reduced so the oxidation state decreases.

When the elements release electrons, the element is oxidized so the oxidation state increases.

We have to think, that global charge of a compound is 0, for example in the ZnSO₄.

The sulfate anion has a global charge of -2 because it has released 2 protons, it came from the sulfuric acid (H₂SO₄). As the global charge is -2, oxygen acts with -2, and the anion has 4 atoms so the global charge of O is -8. Definetly S, has +6 as oxidation state.

In the SO₂, oxygen acts with -2 and there are 2 atoms in the compound, so the global charge is 0 and the global charge for O is -4. Therefore S must act with +4.

Ba²⁺ is an element of group 2 and has a tendency to form a cation, so it can release electrons for that purpose. At least, it can release 2 e⁻, that's why the oxidation state is +2. It can complete the octet rule and it will be isoelectronic with Xe.

3 0

3 years ago