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photoshop1234 [79]
3 years ago
5

What is the melting point of a solution in which 2.5 grams of sodium chloride is added to 230 mL of water?

Chemistry
1 answer:
Lemur [1.5K]3 years ago
5 0
To get the melting point of a solution so, we will use this formula:

ΔT = - mKf

when:

m is molality of the solution

Kf is cryoscopic constant  of water  = 1.86 C/m

and ΔT is the change in melting point (T2 - 0 °C)

so, now we need to calculate the molality to substitute:

when the molality = moles NaCl / Kg of water

 and when moles NaCl  = mass / molar mass

                                       = 2.5 g / 58 g/mol

                                       = 0.043 mol
∴ Kg water = volume *density /1000

                   = 230 mL * 1 g/mL / 1000

                  = 0.23 Kg
∴ molality = 0.043 / 0.23 =0.187 M

by substitution:

T2-0°C = - 0.187 * 1.86

∴T2 = - 0.348 °C

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Answer:

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Explanation:

The following were obtained from the question:

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What is the theoretical yield of a reaction?
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Hydrazine (N2H4) is used as rocket fuel. It reacts with oxygen to form nitrogen and water.
Marina86 [1]

Answer:

See explanation below for answers

Explanation:

This is a stochiometry reaction. LEt's write the overall reaction again:

N₂H₄ + O₂ ---------> N₂ + 2H₂O

This reaction is taking place at Standard temperature and pressure conditions (STP) which are P = 1 atm and T = 273 K.  To know the volume of N₂ formed, we need to know first how many moles are formed, and this can be calculated with the reagents and the limiting reagent. Let's calculate the moles first of the reagents:

MM N₂H₄ = 32 g/mol;    MM O₂ = 32 g/mol

mol N₂H₄ = 2000 / 32 = 62.5 moles

mol O₂ ? 2100 / 32 = 65.63 moles

Now that we have the moles, we need to apply the stochiometry and calculate the limiting reagent. According to the overall reaction we have a mole ratio of 1:1 between N₂H₄ and O₂, therefore:

1 mole N₂H₄ ---------> 1 mole O₂

62.5 moles ----------> X

X = 62.5 moles of O₂

But we have 65.63 moles, therefore, the limiting reactant is the N₂H₄.

We also have a 1:1 mole ratio with the N₂, so:

moles N₂H₄ = moles N₂ = 62.5 moles

Now that we have the moles, we can calculate the volume with the ideal gas equation:

PV = nRT

V = nRT / P

R: gas constant (0.082 L atm / K mol)

Replacing we have:

v = 62.5 * 0.082 * 273 / 1

V = 1399.13 L of N₂

Now, how many grams of the excess remains?, we know how many moles are reacting so, let's see how much is left:

moles remaining = 65.63 - 62.5 = 3.12 moles

then the mass of oxygen:

m = 3.12 * 32 = 100.16 g of O₂

7 0
3 years ago
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