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Andrei [34K]
3 years ago
5

Please help in Chemistry!!!! 15 points! I added a picture below...

Chemistry
2 answers:
aleksandr82 [10.1K]3 years ago
7 0
Yeah, the answer would be choice B because it drops from 40 to 20 so it's -20
krek1111 [17]3 years ago
5 0
The answer would be choice B because the energy decreased by 20 J
You might be interested in
A compound is 42.9% C, 2.4% H, 16.7% N, and 38.1% O, by mass. Addition of 6.45 g of this compound to 50.0 mL benzene, lowers the
Romashka [77]

This is an incomplete question, here is a complete question.

A compound is 42.9% C, 2.4% H, 16.7% N and 38.1% O by mass. Addition of 6.45 g of this compound to 50.0 mL benzene, C₆H₆ (d= 0.879 g/mL; Kf= 5.12 degrees Celsius/m), lowers the freezing point from 5.53 to 1.37 degrees Celsius. What is the molecular formula of this compound?

Answer : The molecular of the compound is, C_6H_4N_2O_4

Explanation :

First we have to calculate the mass of benzene.

\text{Mass of benzene}=\text{Density of benzene}\times \text{Volume of benzene}

\text{Mass of benzene}=0.879g/mL\times 50.0mL=43.95g

Now we have to calculate the molar mass of unknown compound.

Given:

Mass of unknown compound (solute) = 6.45 g

Mass of benzene (solvent) = 43.95 g  = 0.04395 kg

Formula used :  

\Delta T_f=K_f\times m\\\\\Delta T_f=K_f\times\frac{\text{Mass of unknown compound}}{\text{Molar mass of unknown compound}\times \text{Mass of benzene in Kg}}

where,

\Delta T_f = change in freezing point  = 5.53-1.37=4.16^oC

\Delta T_s = freezing point of solution

\Delta T^o = freezing point of benzene

Molal-freezing-point-depression constant (K_f) for benzene = 5.12^oC/m

m = molality

Now put all the given values in this formula, we get

4.16^oC=(5.12^oC/m)\times \frac{6.45g}{\text{Molar mass of unknown compound}\times 0.04395kg}

\text{Molar mass of unknown compound}=180.6g/mol

If percentage are given then we are taking total mass is 100 grams.

So, the mass of each element is equal to the percentage given.

Mass of C = 42.9 g

Mass of H = 2.4 g

Mass of N = 16.7 g

Mass of O = 38.1 g

Molar mass of C = 12 g/mole

Molar mass of H = 1 g/mole

Molar mass of N = 14 g/mole

Molar mass of O = 16 g/mole

Step 1 : convert given masses into moles.

Moles of C = \frac{\text{ given mass of C}}{\text{ molar mass of C}}= \frac{42.9g}{12g/mole}=3.575moles

Moles of H = \frac{\text{ given mass of H}}{\text{ molar mass of H}}= \frac{2.4g}{1g/mole}=2.4moles

Moles of N = \frac{\text{ given mass of N}}{\text{ molar mass of N}}= \frac{16.7g}{14g/mole}=1.193moles

Moles of O = \frac{\text{ given mass of O}}{\text{ molar mass of O}}= \frac{38.1g}{16g/mole}=2.381moles

Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.

For C = \frac{3.575}{1.193}=2.99\approx 3

For H = \frac{2.4}{1.193}=2.01\approx 2

For N = \frac{1.193}{1.193}=1

For O = \frac{2.381}{1.193}=1.99\approx 2

The ratio of C : H : N : O = 3 : 2 : 1 : 2

The mole ratio of the element is represented by subscripts in empirical formula.

The Empirical formula = C_3H_2N_1O_2

The empirical formula weight = 3(12) + 2(1) + 1(14) + 2(16) = 84 gram/eq

Now we have to calculate the molecular formula of the compound.

Formula used :

n=\frac{\text{Molecular formula}}{\text{Empirical formula weight}}

n=\frac{180.6}{84}=2

Molecular formula = (C_3H_2N_1O_2)_n=(C_3H_2N_1O_2)_2=C_6H_4N_2O_4

Therefore, the molecular of the compound is, C_6H_4N_2O_4

3 0
3 years ago
Long ago, living things were divided into two main groups: _________
solmaris [256]

Answer:

I think the answer is Prokaryote and Eukaryote

Explanation:

6 0
3 years ago
How do water molecules move away from their H-O-H configuration to become new molecules?
maksim [4K]

Answer:

A water molecule is consists of two hydrogen atom, each bound to the central oxygen atom through a covalent chemical bond.

Water molecules can form new molecules by moving away from their H-O-H configuration due to thermal motions and rotations. <u>Thermal motions and rotations break the individual hydrogen bonds and change the  H-O-H configuration influenced by the temperature and pressure.</u>

<u />

7 0
3 years ago
How to balance the question?​
umka21 [38]

Answer:

CH4 + 2O2 —> CO2 + 2H2O

CH4 + 2O2

C = 1

H = 4

O = 2 ×2 = 4

__o_o___

CO2 + 2H20

C = 1

H = 2 × 2 = 4

O = 2 + 2 = 4

So ; 1 C , 4 H , 4 O

I hope I helped you^_^

4 0
3 years ago
Why are redox reactions used in batteries?
Phoenix [80]

Answer:

Why are redox reactions used in batteries? The attraction between charged ions releases energy. The movement of electrons creates an electric current. The reactions are extremely exothermic, producing an electric current.

Explanation:

Why are redox reactions used in batteries?

The attraction between charged ions releases energy.

The movement of electrons creates an electric current.

The reactions are extremely exothermic, producing an electric current.

The reactions are extremely endothermic, inducing the movement of electrons.

5 0
3 years ago
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