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Daniel [21]
3 years ago
6

An aqueous solution containing 17.5 g of an unknown molecular (nonelectrolyte) compound in 100.0 g of water has a freezing point

of -1.8 degrees C. Calculate the molar mass of the unknown compound.
Chemistry
1 answer:
Sonbull [250]3 years ago
6 0

Answer:

molar mass = 180.833 g/mol

Explanation:

  • mass sln = mass solute + mass solvent

∴  solute: unknown molecular (nonelectrolyte)

∴ solvent: water

∴ mass solute = 17.5 g

∴ mass solvent =  100.0 g = 0.1 Kg

⇒ mass sln = 117.5 g

freezing point:

  • ΔTc = - Kc×m

∴ ΔTc = -1.8 °C

∴ Kc H2O = 1.86 °C.Kg/mol

∴ m: molality (mol solute/Kg solvent)

⇒ m = ( - 1.8 °C)/( - 1.86 °C.Kg/mol)

⇒ m = 0.9677 mol solute/Kg solvent

  • molar mass (Mw) [=] g/mol

∴ mol solute = ( m )×(Kg solvent)

⇒ mol solute = ( 0.9677 mol/Kg) × ( 0.100 Kg H2O )

⇒ mol solute = 0.09677 mol

⇒ Mw solute = ( 17.5 g ) / ( 0.09677 mol )

⇒ Mw solute = 180.833 g/mol

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The charge that 3 protons, 3 neutrons and 2 electrons have is that it will be a cation of Li with a charge of +1.

Li^+1.
6 0
3 years ago
Emily wanted to see what battery lasted the longest. She put each battery into a clock and recorded the time that the clock stop
Andru [333]

Answer:

independent variable -- different batteries

dependent variable -- the time that clock stop

Explanation:

In an experiment or a research study, there are two type of variables that can affect the result of the experiment or the conclusion. They are independent variable and the dependent variable.

An independent variable may be defined as that variable in an experiment which can be changed or can be controlled in the scientific experiment in order to test the effect on the dependent variable. It cannot be changed by other variables.

On the other hand, dependent variable are those are those which can be altered or change that can affect the experiment.

In the context, Emily uses  the different types of the batteries as an independent variable and the time where the clock stopped in the dependent variable in her research.

6 0
3 years ago
How many atoms are in 5 mole of water?<br> Steps
Vladimir79 [104]

Answer: 3.01 x 10^24 atoms

Explanation:

Based on Avogadro's law:

1 mole of any substance has 6.02 x 10^23 atoms

So, 1 mole of water = 6.02 x 10^23 atoms

5 moles of water = Z atoms

To get the value of Z, cross multiply

Z x 1 mole = (6.02 x 10^23 atoms x 5 moles)

Z•mole = 30.1 x 10^23 atoms•mole

Divide both sides by 1 mole

Z•mole/1 mole = 30.1 x 10^23 atoms•mole/ 1 mole

Z = 30.1 x 10^23 atoms

[Place the value of Z in standard form]

Z = 3.01 x 10^24 atoms

Thus, there are 3.01 x 10^24 atoms in 5 mole of water

3 0
3 years ago
How many grams of NaCl (molecular weight = 58 Da) would you have to dissolve in 50ml to make a 2M stock solution? Answer:
Lerok [7]

Answer:

5.8 g

Explanation:

Molecular weight in Daltons is equivalent to the molecular weight in grams per mole.

The amount of NaCl required is calculated as follows:

(2 mol/L)(50 mL)(1 L/1000 mL) = 0.1 mol

This amount is converted to grams using the molar mass (58 g/mol).

(0.1 mol)(58 g/mol) = 5.8 g

7 0
3 years ago
How many moles of H2O form when 4.5 moles O2 reacts?
mart [117]

Explanation:

Start with a balanced equation.

2H2 + O2 → 2H2O

Assuming that H2 is in excess, multiply the given moles H2O by the mole ratio between O2 and H2O in the balanced equation so that moles H2O cancel.

5 mol H2O × (1 mol O2/2 mol H2O) = 2.5 mol O2

Answer: 2.5 mol O2 are needed to make 5 mol H2O, assuming H2 is in excess.

4 0
3 years ago
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