1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Ainat [17]
3 years ago
12

A certain substance X has a normal boiling point of 117.8°C and a molal boiling point elevation constant =Kb·0.63°C·kgmol−1. A s

olution is prepared by dissolving some urea NH22CO in 900.g of X. This solution boils at 118.3°C. Calculate the mass of urea that was dissolved. Round your answer to 1 significant digit.
Chemistry
1 answer:
OlgaM077 [116]3 years ago
5 0

Answer:

42.8 g was the mass of dissolved urea.

Explanation:

Boiling point elevation to solve this:

ΔT = Kb . m

where ΔT → Boiling T° of solution - Boiling T° of pure solvent

Let's replace the data given:

118.3°C - 117.8°C = 0.63°C/m . m

0.5°C / 0.63 m/°C = m → 0.793 mol/kg

Mass of solvent → 900 g → g to kg → 900 g . 1kg/1000 = 0.9 kg

Molality . kg = moles → 0.793 mol/kg . 0.9 kg = 0.714 mol

These are the moles of urea we used. Let's determine the mass dissolved.

0.714 mol . 60 g /1mol = 42.8 g

You might be interested in
A cable raises a mass of 158.0 kg with an acceleration of 1.8 m/s2. What force (in N) of tension is in the cable?
ki77a [65]

Answer:

Force of Tension = 1832.8  N

Explanation:

Any mass of object supported or pulled by a rope or cable  is subject to a force of tension. Since the mass is raised by a cable, tension is involved.

Mathematically,

Tension = mass × gravity(9.8 m/s²)

Tension can be represented as

T = (m × g) + (m × a)

Where g is the acceleration due to gravity of the object the cable is supporting and a is the acceleration on the object the cable is supporting. And m is the mass of the object.

mass = 158 kg

a = 1.8 m/s²

g = 9.8 m/s²

T = mg + ma

T = m(g + a)

T = 158(9.8 + 1.8)

T = 158 × 11.6

T = 1832.8  N

8 0
3 years ago
Explain what occurs in a substitution reaction and give an example of substitution reaction. Explain why organic reactions are t
uranmaximum [27]
Substitution Reactions are those reactions in which one nucleophile replaces another nucleophile present on a substrate. These reactions can take place via two different mechanism i.e SN¹ or SN². In SN¹ substitution reactions the leaving group leaves first forming a carbocation and nucleophile attacks carbocation in the second step. While in SN² reactions the addition of Nucleophile and leaving of leaving group take place simultaneously. 

Example:
                        OH⁻  +  CH₃-Br     →     CH₃-OH  +  Br⁻

In above reaction,

                   OH⁻  = Incoming Nucleophile

                   CH₃-Br  =  Substrate

                   CH₃-OH  =  Product

                   Br⁻  =  Leaving group

Organic reactions are typically slower than ionic reactions because in organic compounds the covalent bonds are first broken, this breaking of bonds is a slower step, while, in ionic compounds no bond breakage is required as it consists of ions, so only bond formation takes place which is a quicker and fast step.
7 0
3 years ago
What does conserving mass mean in a chemical equation?
expeople1 [14]
The correct answer should be letter choice C) There is an equal number of each type of atom on the reactant and product side. Its C) because if its trying to conserve mass, than that means save or be equally balanced so it should be even for both sides.


7 0
3 years ago
How many moles are in 25.0 grams of KMnO4?
Lilit [14]

Answer:- 0.158 moles

Solution:- Moles are calculated on dividing the grams by the molar mass.

25.0 grams of KMnO_4 are given and we are asked to calculate the moles.

For this we need the molar mass so let's calculate it first.

Molar mass is the sum of atomic masses of all the atoms present in the molecule.

Molar mass = 39.098+54.938+4(16)

= 158.036 gram per mol

Now, we will divide the given grams by molar mass to get the moles and the set is shown as:

25.0gKMnO_4(\frac{1mol}{158.036g})

= 0.158molKMnO_4

So, there are 0.158 moles of KMnO_4 .

3 0
3 years ago
How many electrons will the lithium atom give up to become stable?
Angelina_Jolie [31]
Recall that most atoms are stable when their outermost ring has eight electrons. (Some atoms, such as lithium and beryllium, are stable when their outermost ring has two electrons.)
8 0
2 years ago
Read 2 more answers
Other questions:
  • The reduced coenzymes generated by the citric acid cycle donate electrons in a series of reactions called the electron transport
    15·1 answer
  • A sample of hydrogen gas has an initial pressure of 2.86 atm and an initial volume of 8472 mL If the volume of the
    15·1 answer
  • How is an invasive species introduced to a new ecosystem? An invasive species is introduced to an ecosystem through a _______
    10·2 answers
  • Melted rock can ooze out from below earths surface through a crack in the crust called a(n)?
    10·1 answer
  • Use the periodic table to identify the element with the electron configuration 1s²2s²2p⁴. Write its orbital diagram, and give th
    14·1 answer
  • A sample of nitrogen occupies 10.0 liters at 25°c and 98.7 kpa. What would be the volume at 20°c and 102.7 kpa?
    15·1 answer
  • Differences between plant and animal cells, other than their vacuoles
    9·1 answer
  • A block of ice has little thermal energy. If you place it in a warm room, it melts into warm liquid water, which has much more e
    7·1 answer
  • The process of asking questions is known as
    13·2 answers
  • Select the correct answer. Why is it important to include recovery time in a workout program? A. It prevents you from getting bo
    15·2 answers
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!