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wel
3 years ago
5

Adding 5.25 g of to 130 g of water in a coffee-cup calorimeter (with stirring to dissolve the salt) resulted in a decrease in te

mperature from 18.1 °C to 15.4 °C. Calculate the enthalpy change for dissolving in water in kJ/mol. Assume the solution (whose mass is 135.3 g) has a specific heat capacity of 4.2 J/g · K. (Cold packs take advantage of the fact that dissolving ammonium nitrate in water is an endothermic process.)
Chemistry
1 answer:
xxTIMURxx [149]3 years ago
4 0

Answer:

ΔHrxn =  - 1534.3 J

Explanation:

Given the assumptions and the formula for the change in enthalpy:

ΔHrxn = m x C x ΔT,  where

               m is the mass of solution given 135.4 g

               C is the heat capacity 4.2 J/g .K  and,

               ΔT is the change in temperature

we have ,

T₁ = ( 18.1 + 273) K = 291.1 K

T₂ = ( 15.4 +273) K = 288.4 K

ΔHrxn =  135.3 g x 4.2 J/gK x ( 288.4 -291.1 ) K = - 1534.3 J

After verifying our result has the correct unit, the answer is -1534.3 Joules, and the negative sign tells us it is an endothermic reaction decreasing the final temperature.

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What volume of 0.194 MNa3PO4 solution is necessary to completely react with 85.5 mL of 0.109 MCuCl2 ?
ira [324]

Answer:

35.9 ml

Explanation:

Start with the balanced equation:

3CuCl2(aq)+2Na3PO4(aq)→Cu3(PO4)2(s)+6NaCl(aq)

This tells us that 3 moles of CuCI2 react with 2 moles Na3PO4-

∴  1 mole CuCl2 will react with 2/3 moles Na3PO4

We know that concentration = moles/volume i.e:

c= n/v

∴n=c×v

∴nCuCl2=0.107×91.01000=9.737×10−3

I divided by 1000 to convert ml to L

∴nNa3PO4=9.737×10−3×23=6.491×10−3

v=nc=6.491×10−30.181=35.86×10−3L

∴v=35.86ml

4 0
2 years ago
I will give brainliest (8th grade)
lesya [120]

Answer:

2.The cooling effects of more indirect sunlight cause autumn and winter. Because of the Earth's approximately 23.5º tilt, the seasons in the Northern and Southern Hemispheres are reversed, about six months apart from each other.

3.In North America, around June 21, Earth tilts on its axis toward the Sun. That means that at the northern summer solstice, North America will experience summer, and winter will start in in the Southern Hemisphere. Winter Solstice. Around December 21, the Northern Hemisphere tilts the farthest away from the Sun.

Explanation:

3 0
3 years ago
Write the net ionic equation for the reaction of aqueous solutions of ammonium chloride and iron(III) hydroxide.
vagabundo [1.1K]

Answer:

Fe(OH)_3(s)\rightarrow Fe^{3+}(aq)+3OH^-(aq)

Explanation:

Hello.

In this case, for the reaction between aqueous solutions of ammonium chloride and iron (III) hydroxide, we have the following complete molecular reaction:

3NH_4Cl(aq)+Fe(OH)_3(s)\rightarrow 3NH_4OH+FeCl_3

And the full ionic equation, taking into account that the iron (III) hydroxide cannot be dissolved as it is insoluble in water:

3NH_4^+(aq)+3Cl^-(aq)+Fe(OH)_3(s)\rightarrow 3NH_4^+(aq)+3OH^-(aq)+Fe^{3+}(aq)+3Cl^-(aq)

Finally, the net ionic equation, considering that spectator ions are NH₄⁺, Cl⁻ as they are both the left and right side, therefore, the net ionic equation is:

Fe(OH)_3(s)\rightarrow Fe^{3+}(aq)+3OH^-(aq)

Best regards.

8 0
3 years ago
how many grams of calcium sulfate are produced from 10 grams of calcium nitrate and how many grams of calcium sulfate are produc
AlekseyPX

Answer:  8.30 g of calcium sulfate are produced from 10 grams of lithium sulfate.

Explanation:

To calculate the moles :

\text{Moles of solute}=\frac{\text{given mass}}{\text{Molar Mass}}    

\text{Moles of} Ca(NO_3)_2=\frac{10g}{164g/mol}=0.061moles

\text{Moles of} Li_2SO_4=\frac{10g}{110g/mol}=0.091moles

Ca(NO_3)_2+Li_2SO_4\rightarrow 2LiNO_3+CaSO_4  

According to stoichiometry :

1 mole of Ca(NO_3)_2 require = 1 mole of Li_2SO_4

Thus 0.061 moles of Ca(NO_3)_2 will require=\frac{1}{1}\times 0.061=0.061moles  of Li_2SO_4

Thus Ca(NO_3)_2 is the limiting reagent as it limits the formation of product and Li_2SO_4 is the excess reagent.

As 1 mole of Ca(NO_3)_2 give = 1 mole of CaSO_4

Thus 0.061 moles of Ca(NO_3)_2 give =\frac{1}{1}\times 0.061=0.061moles  of CaSO_4

Mass of CaSO_4=moles\times {\text {Molar mass}}=0.061moles\times 136g/mol=8.30g

Thus 8.30 g of calcium sulfate are produced from 10 grams of lithium sulfate.

6 0
3 years ago
Jim drops an iron magnet during a chemistry lab experiment. He finds that it is no longer magnetic. What has happened in terms o
jok3333 [9.3K]

Answer: option A.

A physical change occurred in which the iron remained iron, but lost one of its physical properties

Explanation: magnetization and demagnetization is a physical change as no new substance is form and it is easily reversed. When an iron rod is magnetized, it can loss it magnetic property by hitting it. So when an iron rod which is magnetized falls from a height it can also loss its magnetic property

4 0
3 years ago
Read 2 more answers
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