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miv72 [106K]
2 years ago
9

OVER 200 POINTS- THIS QUESTION IS POSTED TWICE ON MY PROFILE FOR 100 POINTS EACH AND IT IS POSTED A COUPLE TIMES FOR 30 POINTS.

IF YOU KNOW THE ANSWER YOU CAN PUT IT ON ALL THE POSTS AND GET ALL THE POINTS I JUST REALLY NEED HELP. THANKS!
A student dissolves 0.250 mol NaC1 in 2.05 kg H20. What is the molality of the resulting solution? Show your work.
Chemistry
1 answer:
Natali5045456 [20]2 years ago
7 0

Answer:

The molality ( m ) of a solution is the moles of solute divided by the kilograms of solvent. A solution that contains 1.0 mol of NaCl dissolved into 1.0 kg of water is a “one-molal” solution of sodium chloride. The symbol for molality is a lower-case m written in italics.

In order to calculate the molality of a solution divide the moles of solute by the volume of the solution expressed in liters.

I did what I think you meant if it's wrong text me I'll fix it.

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Which element can expand its valence shell to accommodate more than eight electrons? which element can expand its valence shell
Anvisha [2.4K]
<span>According to octet rule,  atoms with an atomic number less than 20 tend to combine  with other atom such that both of these atoms have eight electrons in their valence shells, which gives them the same electronic configuration as that of noble gas.

However, there are few compound that donot obey octel rule. Among the elements mentioned above i.e. oxygen and helium obeys octet rule.

In case of nitrogen, oxide of nitrogen (like NO and NO2) have incomplete octet. 

While there are few compounds of Br wherein Br has expanded octet. For example, in BrF5, Br has 12 electrons in valence shell. </span>
3 0
3 years ago
Read 2 more answers
What is the enthalpy for reaction 1 reversed? reaction 1 reversed: co2→co + 12o2 express your answer numerically in kilojoules p
QveST [7]
The enthalpies of formation of each of the compound involved in the chemical reaction presented above are given below:

CO2: -393.5 kJ/mol
CO: -99 kJ/mol
O2: 0 kJ/mol

As observed O2 will not have enthalpy of formation as it is a pure substance. 

To calculate for the enthalpy of reaction,
   enthalpy of formation of products - enthalpy of formation of reactants
= (-99 kJ/mol) - (-393.5 kJ/mol)
    = 294.5 kJ/mol

ANSWER: 294.5 kJ/mol
8 0
3 years ago
Choose the correct option for the redox reaction below : 8H+(aq) + MnO4-(aq) + 5Fe2+(aq) → Mn2+(aq) + 5Fe3+(aq) 4H2O(l) H+ (oxid
hodyreva [135]

Explanation:

8H+(aq) + MnO4-(aq) + 5Fe2+(aq) → Mn2+(aq) + 5Fe3+(aq) + 4H2O(l)

To determine if a substance was reduced or oxidized, the oxidation number at the reactant and product side is compared.

When oxidation occurs, an element loses electrons and its oxidation number increases (becomes more positive). When reduction occurs, an element gains electrons and its oxidation number decreases or is reduced (becomes more negative).

H+ (oxidized or reduced) Answer 1 Choose...

There is an increase in oxidation number from 0 to 1. This means H+ was oxidized.

MnO4- (oxidizing or reducing agent) Answer 2 Choose...

In chemistry, an oxidizing agent is a substance that has the ability to oxidize other substances — in other words to accept their electrons

MnO4- is a strong oxidizing agent.

Fe2+ (oxidizing or reducing agent) Answer 3 Choose...

A reducing agent means it will itself get oxidized. In  this reaction, Fe2+ is the reducing agent.

Fe2+ (oxidized or reduced) Answer 4 Choose...

Oxidized

O in MnO4- (oxidized or reduced) Answer 5 Choose...

There is no change in oxidation number of , so it was neither reduced nor was it oxidized.

Mn in MnO4- (oxidized or reduced) Answer 6 Choose...

There is a decreaase in oxidation number from +7 to +2. This means reduction.

6 0
3 years ago
Question 25———-A, YA are two isotopes of element A.
lakkis [162]

Answer:

Option C. 1

Explanation:

Step 1:

Determination of the Neutron of both isotopes. This is illustrated below.

For isotope y xA:

Mass number = y

Atomic number = x

Neutron =..?

Atomic number = proton number = x

Mass number = Proton + Neutron

y = x + Neutron

Rearrange

Neutron = y – x

For isotope (y + 1) xA:

Mass number = y + 1

Atomic number = x

Neutron =.?

Atomic number = proton number = x

Mass number = Proton + Neutron

y + 1 = x + Neutron

Rearrange

Neutron = y + 1 – x

Step 2:

Determination of the difference between the neutron number of both isotopes. This is illustrated below:

For isotope y xA:

Neutron number = y – x

For isotope (y + 1) xA:

Neutron number = y + 1 – x

Difference in neutron number

=> (y + 1 – x) – (y – x)

=> y + 1 – x – y + x

Rearrange

=> y – y + 1 – x + x

=> 1

Therefore, the difference in the neutron number of both isotopes is 1

6 0
3 years ago
The rate of a chemical reaction may be defined as Select one: a. the time it takes for the reaction to be completed b. the chang
kaheart [24]
It is A. This is because the rate of reaction is defined as the speed at which the reactants are converted into the products.
8 0
2 years ago
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