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timofeeve [1]
3 years ago
10

BRAINLIESTTT ASAP!! PLEASE HELP ME :)

Chemistry
1 answer:
alexandr402 [8]3 years ago
3 0

Physical change is the change we can see with our eyes. Chemical change is the change that we cannot see. Examples: physical change: The Polar ice caps are melting, and we can see that as it happens. Chemical change: The cooking of an egg or some combustion, like a fire. We can't see the chemicals coming from the fire, but there are chemicals coming from what is being burned and is being released into the air that we cannot see.

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A student dissolves 15.0 g of ammonium chloride(NH4Cl) in 250. 0 g of water in a well-insulated open cup. She then observes the
iren2701 [21]

Answer:  

1) Endothermic.  

2) Q_{rxn}=4435.04J  

3) \Delta _rH=15.8kJ/mol

Explanation:  

Hello there!  

1) In this case, for these calorimetry problems, we can realize that since the temperature decreases the reaction is endothermic because it is absorbing heat from the solution, that is why the temperature goes from 22.00 °C to 16.0°C.  

2) Now, for the total heat released by the reaction, we first need to assume that all of it is released by the solution since it is possible to assume that the calorimeter is perfectly isolated. In such a way, it is also valid to assume that the specific heat of the solution is 4.184 J/(g°C) as it is mostly water, therefore, the heat released by the reaction is:

Q_{rxn}=-(15.0g+250.0g)*4.184\frac{J}{g\°C}(16.0-20.0)\°C\\\\ Q_{rxn}=4435.04J    

3) Finally, since the enthalpy of reaction is calculated by dividing the heat released by the reaction over the moles of the solute, in this case NH4Cl, we proceed as follows:

\Delta _rH=\frac{ Q_{rxn}}{n}\\\\\Delta _rH= \frac{ 4435.04J}{15.0g*\frac{1mol}{53.49g} } *\frac{1kJ}{1000J} \\\\\Delta _rH=15.8kJ/mol

Best regards!  

Best regards!

4 0
2 years ago
Which of these figures probably shows a sugar solution containing a small amount of sugar dissolved in water
Vesnalui [34]

Answer:

The correct answer is Sugar has a greater solubility than sand.

Sugar will easily dissolve in water because it has a lower density than sand, therefore it has a greater solubility.

8 0
3 years ago
Read 2 more answers
List the four groups attached to the central carbon of an amino acid.
IrinaVladis [17]
Structure of an Amino Acid. Amino acids are the monomers that make up proteins. Each amino acid has the same fundamental structure , which consists of a central carbon atom, also known as the alpha (α) carbon, bonded to an amino group (NH 2), a carboxyl group (COOH), and to a hydrogen atom.
4 0
3 years ago
Read 2 more answers
Which of the following chemical formulas show three molecules of a compound that has one
mr_godi [17]

The chemical formula : 3HgBr₂(Mercury(II) bromide)

<h3>Further explanation</h3>

Given

The chemical formulas of Mercury and Bromine

Required

The appropriate chemical formula

Solution

A molecular formula is a formula that shows the number of atomic elements that make up a compound.  

The number of molecules is determined by the coefficient in front of the compound

the number of atoms is determined by the subscript after the atom and the coefficient

Three molecules⇒ coefficient = 3

one atom of Mercury ⇒Hg

two atoms of Bromine ⇒ Br₂

The chemical formula : 3HgBr₂

6 0
2 years ago
Velocity is a vector quantity.Why?​
Alika [10]

Answer:

Has size and magnitude whereas a scalar quantity has only size

3 0
2 years ago
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