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Triss [41]
3 years ago
11

. Calculate the molality of each of the following solutions: (a) 0.710 kg of sodium carbonate (washing soda), Na2CO3, in 10.0 kg

of water—a saturated solution at 0°C (b) 125 g of NH4NO3 in 275 g of water—a mixture used to make an instant ice pack (c) 25 g of Cl2 in 125 g of dichloromethane, CH2Cl2 (d) 0.372 g of histamine, C5H9N, in 125 g of chloroform, CHCl3
Chemistry
1 answer:
Step2247 [10]3 years ago
4 0

Answer:

a)0.67 molal

b) 5.67 molal

c) 2.82 molal

d) 0.0268 molal

Explanation:

Step 1: Data given

Molality = moles solute / mass solvent

(a) 0.710 kg of sodium carbonate (washing soda), Na2CO3, in 10.0 kg of water—a saturated solution at 0°C

Calculate moles of Na2CO3 =  710 grams / 105.99 g/mol = 6.70 moles

Molality = 6.70 moles / 10 kg = 0.67 molal

(b) 125 g of NH4NO3 in 275 g of water—a mixture used to make an instant ice pack

Calculate moles of NH4NO3 = 125 grams / 80.04 g/mol = 1.56 moles

molality = 1.56 moles / 0.275 kg = 5.67 molal

(c) 25 g of Cl2 in 125 g of dichloromethane, CH2Cl2

Calculate moles Cl2 = 25 grams / 70.9 g/mol= 0.353 moles

Molality = 0.353 moles / 0.125 kg = 2.82 molal

0.372 g of histamine, C5H9N, in 125 g of chloroform, CHCl3

Calculate moles histamine = 0.372 grams / 111.15 g/moles = 0.00335 moles

Calculate molality = 0.00335 moles / 0.125 kg = 0.0268 molal

NOTE: histamine is C5H9N3 not C5H9N

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S_A_V [24]

Answer:

44.91% of Oxygen in Iron (III) hydroxide

Explanation:

To solve this question we must find the molar mass of Fe(OH)3 and the molar mass of the oxygen in this molecule. Percent composition will be:

<em>Molar mass Oxygen / molar mass Fe(OH)3 * 100</em>

<em />

<em>Molar mass Fe(OH)3 and oxygen:</em>

1Fe = 55.845g/mol*1 = 55.845

3O = 16.00g/mol*3 = 48.00 - Molar mass of Oxygen

3H = 1.008g/mol*3 = 3.024

55.845 + 48.00 + 3.024 =

106.869g/mol is molar mass of Fe(OH)3

% Composition of oxygen is:

48.00g/mol / 106.869g/mol * 100 =

<h3>44.91% of Oxygen in Iron (III) hydroxide</h3>
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What is the correct order of steps to determine the mass of product created, given a certain mass of reactant?
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Explanation:

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4. When 1.00 L of 1.00 M Ba(NO3)2 solution at 25.0˚C is mixed with 1.00 L of 1.00 M Na2SO4 solution at 25.0˚C in a calorimeter,
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Answer:

The final temperature of the mixture is 28.11 °C

Explanation:

Step 1: Data given

Volume of 1.00 M Ba(NO3)2 = 1.00 L

Temperature = 25.0 °C

Volume of 1.00 M Na2SO4 = 1.00 L

enthalpy change is – 26 kJ per mol BaSO4

The specific heat of water is 4.18 J/g ·˚C

the density of water is 1.00 g/mL

Step 2: The balanced equation

Ba(NO3)2(aq) + Na2SO4(aq) → 2NaNO3(aq) + BaSO4(s)

Step 3: Calculate the total volume

Total volume = 1.00 L + 1.00 L = 2.00 L = 2000 mL

Step 4: Calculate mass

Mass = volume * density

Mass = 2000 mL * 1g/mL

Mass = 2000 grams

Step 5: Calculate moles BaSO4 formed

For 1 mol Ba(NO3)2 we need 1 mol Na2SO4 to produce 1 mol BaSO4

There is no limiting reactant, both Ba(NO3)2 and Na2SO4 will be completely be consumed (1 mol). We'll have 1.0 mol of BaSO4 produced.

Step 6: Calculate Q

Q = - ΔH

ΔH is negative so the reaction is exothermic, what means the temperature increases

Q is always positive, so Q = 26kJ = 26000 J

Step 6: Calculate the heat transfer

Q= m*c*ΔT

⇒with Q = the heat transfer = TO BE DETERMINED

⇒with m =the mass of the solution = 2000 grams

⇒with c= the specific heat of the solution = 4.18 J/g°C

⇒with ΔT = the change of temperature = T2 - T1 = T2 - 25.0

26000 = 2000 * 4.18 * (T2 - 25.0 °C)

3.11 = T2 - 25.0 °C

T2 = 25.0 + 3.11 °C

T2 = 28.11 °C

The final temperature of the mixture is 28.11 °C

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Answer:

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Explanation:

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