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Serga [27]
3 years ago
10

in order to find the molar mass of an unknown compound, a research scientist prepared a solution of 0.930 g of an unknown in 125

g of a solvent. The pure solvent had a freezing point of 74.2 degrees celcius, and the solution had a freezing point of 73.4 degrees celcius. Given the solvents freezing point depreesion contant, Kf=5.50 degrees celcius/m, find the molar mass of the unknown
Chemistry
1 answer:
PtichkaEL [24]3 years ago
3 0

Answer:

Molar mass→ 0.930 g / 6.45×10⁻³ mol = 144.15 g/mol

Explanation:

Let's apply the formula for freezing point depression:

ΔT = Kf . m

ΔT = 74.2°C - 73.4°C → 0.8°C

Difference between the freezing T° of pure solvent and freezing T° of solution

Kf = Cryoscopic constant → 5.5°C/m

So, if we replace in the formula

ΔT = Kf . m → ΔT / Kf = m

0.8°C / 5.5 m/°C = m → 0.0516 mol/kg

These are the moles in 1 kg of solvent so let's find out the moles in our mass of solvent which is 0.125 kg

0.0516 mol/kg . 0.125 kg = 6.45×10⁻³ moles. Now we can determine the molar mass:

Molar mass (mol/kg) → 0.930 g / 6.45×10⁻³ mol = 144.15 g/mol

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3 years ago
Methionine, ch3sch2ch2ch(nh2)co2h, is an amino acid found in proteins. what is the hybridization type of each carbon, oxygen, th
Lady_Fox [76]
Answer 1) To find the hybridization of carbon we need to draw the lewis structure first; which is attached in the answer.

So the formula for finding hybridization is 
Lone pairs + Bonding pairs = hybridisation.

Here, in the molecule of methionine Carbon is bonded to all 4 atoms and has got no lone pairs so we will have;

0 + 4 = 4 which means it is sp^{3} hybridized.

Answer 2) For oxygen we can see in the lewis structure that it is having 2 lone pairs and double bonded with carbon atom, also there is another oxygen atom with two lone pair but bonded with carbon and hydrogen at the end.

So, in both the cases we can calculate;

where 2 lone pairs are present  
2 + 2 = 4 so, it will be sp^{3} hybridized.

So, Oxygen is also sp^{3} hybridized.

Answer 3) Nitrogen present in the methionine is bonded to carbon atom and hydrogen atoms and has only one lone pair on it.

So when we are substituting this in the formula we get 1 + 3 = 4;

which means 1 lone pair and 3 bond pairs so, it is also sp^{3} hybridized.

Answer 4) Sulfur atom in methionine is bonded to two carbon atoms forming a linear structure with 2 lone pairs on it.

So, it has 2 lone pairs and 2 bond pairs,

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5 0
3 years ago
Fill In The Blanks:
yawa3891 [41]

Answers : Fill in the blanks.


Answer 1) During a chemical reaction, the sum of the masses of the reactants and products remain unchanged.


In a reaction masses of the reactants and products always remains the same.


Answer 2) In a pure chemical compound, elements are always present in a definite proportion by mass.


It is observed that in a chemical reaction the elements are found in definite proportion by mass.


Answer 3) Clusters of atoms that act as an ion are called polyatomic ions.


Polyatomic ions are those ions which consits of atoms more than two in their molecule.


Answer 4) In ionic compounds, the charge on each ion is used to determine the chemical formula of the compound.


The charges on the molecule helps to determine the chemical formula of any compound.


Answer 5) The Avogadro constant 6.022 X 10^{23} is defined as the number of atoms in exactly 12 g of carbon-12


Avogadro used carbon-12 as the standard reference element fpr determining its molecules.


Answer 6) Mass of 1 mole of a substance is called its molar mass or molecular weight.


A molecular weight of an atom to define its number of moles.


Answer 7) The abbreviation used for length names of elements are termed as their Symbols.


The abbreviation used for the length of names of elements are called as symbols.


Answer 8) A chemical formula is also known as a true formula or molecular formula.


The term chemical formula determines the number of chemical components present in it.

Answer 9) Those ions which are formed from single atoms are called monoatomic ions.


The ions made up from single atoms are called as monoatomic ions.


Answer 10) Ionic compounds are formed by the combination between metal and nonmetal.


The ionic compounds are usually bonded by the ionic bonds in a compound.


Answer 11) The valency of an ion is equal to the charge on the ion.


Valency of any ion is always equal to the charge on that ion.


Answer 12) Mole is a link between the mass of a substance and number of formula units.


Usually the mole forms a link to define the mass of the substance and its formula.


Answer 13) The SI unit of amount of a substance is mole.


Mole is considered to be the SI unit for aount of substance of any chemical compound.

Answer : true or false.


Answer 1) Formula mass of Na_{2}O is 62 amu True


As we know there are 2 moles of Na and one mole of O so it will be (2 X 23) + 16 = 62 amu.


Answer 2) Those particles which have more or less electrons than the normal atoms are called ions True


We call ions to those atoms which hav more or less electrons in their normal atoms


Answer 3) Formula for sulphur dioxide is SO_{3}. False



The formula for sulphur dioxide  is SO_{2} as the name di suggests two molecules.


Answer 4) Molar mass of ethyne (C2H2) is 26 g/mol True.


As the ethyene molecule consists of 2 C atoms and 2 H atoms it will be (12 X 2) + (2 X 1) = 26


Answer 5) 22 gm of CO2 consists of 1 mole. False

 


The 1 mole of CO_{2} contains 1 C atom and 2  O atoms (12) + (16 X 2) = 44


Answer 6) Number of molecules in 32 gram of oxygen is 6.02 x 10^{23}. False


Only 1 moles of any substance will consist of 6.02 x 10^{23} molecules.


Answer 7) Water is an atom False.


Water is a molecule of 2 atoms namely hydrogen and oxygen.


Answer 8) Formula for sulphur dioxide is SO_{2} true.


As the name suggest sulphur along with two oxygen in it.


Answer 9) Clusters of atoms that act as an ion is called polyatomic ion. True


The clusters of ions from different atoms of the elements can be called as polyatomic ions.


Answer 10) Mass of 1 mole of a substance is called its formula mass. False.


As in formula mass we take the sum of the atomic weights of atoms in a molecule. And for 1 mole of a substance it is called as molar mass.


Answer 11) In a pure chemical compound, elements are always present in a definite proportion by mass. True


In any chemical reaction, the pure chemical compound is always found to have elements with definite proportion to their masses.


5 0
3 years ago
How many moles of ethylene (C2H4) can react with 12.9 liters of oxygen gas at 1.2 atmospheres and 297 Kelvin? C2H4(g) + 3O2(g) y
7nadin3 [17]
1) Convert 12.9 liters of Oxygen to mol at the given conditions:

PV = nRT ⇒ n = PV/RT

n = [1.2atm*12.9 l] / [0.082 atm l /K mol * 297K]

n = 0.636 mol of O2

2) use the stoichiometry derived from the balanced chemical equation

 1mol C2H4 / 3  mol O2 =  x mol C2H4 / 0.636 mol O2

x = 0.636 / 3 mol O2 = 0.212 mol O2.

Answer: 0.212 mol O2
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Answer: stay the same because it's a solid.

Explanation:

5 0
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