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notka56 [123]
3 years ago
14

Show the calculation of the final temperature for a 20.8 gram piece of iron heated to 100oC which has been added to a 55.3 gram

sample of water at 25.3oC in a coffee cup calorimeter.
c (water) = 4.184 J/g oC; c (Fe) = 0.449 J/g oC
Chemistry
1 answer:
GrogVix [38]3 years ago
5 0

Answer:

Final Temperature = 28.2 oC

Explanation:

Information given;

Mass of Iron = 20.8g

Initial Temperature of Iron = 100C

Mass of water = 55.3g

Initial temperature of water = 25.3 C

The presence of a coffee cup calorimeter hints that there is no heat loss to the surrounding and that the iron and water are at thermal equilibrium.

Thermal equilibrium means that there is no heat transfer going on between the bodies, which simply means that the bodies are at the same temperature.

Hence, both bodies would the same final temperature (T2)

H = M * C * ΔT (For iron)

H = 20.8 * 0.449 * ( 100 - T2)

H = 9.3392 ( 100 - T2)

H = 933.92 - 9.3392T2

H = M * C * ΔT (For water)

H = 55.3 * 4.184 * (T2 - 25.3)

H = 231.3752 (T2 - 25.3)

H = 231.3752T2 - 5853.79

Since they are in thermal equilibrium it means H (Iron) = H (water).

This leads to;

933.92 - 9.3392T2 = 231.3752T2 - 5853.79

231.3752T2 +  9.3392T2  = 5853.79 + 933.92

240.7144 T2 = 6787.71

T2 = 28.2 oC

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he decomposition of acetaldehyde, CH3CHO, was determined to be a second order reaction with a rate constant of 0.0771 M-1 s-1. I
nataly862011 [7]

Answer:

The concentration is [-1 + sqrt(1+0.11t)]/0.1542 M

Explanation:

Let the concentration of CH3CHO after selected reaction times be y

Rate = Ky^2 = change in concentration of CH3CHO/time

K = 0.0771 M^-1 s^-1

Change in concentration of CH3CHO = 0.358 - y

0.0771y^2 = 0.358-y/t

0.0771ty^2 = 0.358 - y

0.0771ty^2 + y - 0.358 = 0

The value of y must be positive and is obtained in terms of t using the quadratic formula

y = [-1 + sqrt(1^2 -4(0.0771t)(-0.358)]/2(0.0771) = [-1 + sqrt(1+0.11t)]/0.1542 M

6 0
3 years ago
Consider the cell pt | h2 (1 atm); h+ (? m) || hg2cl2(s); cl− (1 m) | hg 2 h+ + 2 e − → h2 e 0 = 0.00 v hg2cl2 + 2 e − → 2 hg +
Dmitry [639]

Answer:

1.39

Explanation:

[Hg2Cl2]= 1M

[H^+] = ????

E°cell= 0.35V

E= 0.268 V

Therefore E for the reaction must -0.082 V

n= 2 moles of electrons

From Nernst Equation:

E= E°cell- 0.0592/n log [Red]/[Ox]

0.0268= 0.35- 0.0592/2 log 1/[Ox]^2

-0.082= -0.0296 log 1/[Ox]^2

log 1/[Ox]^2= 0.082/0.0296

log 1/[Ox]^2= 2.77

1/[Ox]^2=Antilog (2.77)

[Ox]^2=1.698×10^-3

[Ox] = 0.0412 M

But pH= -log [H^+]= -log(0.0412)= 1.385

3 0
3 years ago
Read 2 more answers
An atom X has 2 electrons in its outer orbit. What will it do to form a stable ion?
matrenka [14]

Answer:

In a neutral molecule, the sum of the bonding valance electrons must be equal. So the products of the negative element and its charges and the positive element and its charge must be equal.

Explanation:

C1×N1 = C2×N2

If we have a 3 valance electrons , the 'A' charge will be either +3 or -5 for a full octet and valance electron in 'B' atoms will mostly result in acquisition of additional electrons (2) for an octet and relative charge of -2.

Balancing the two,

3 × A = -2 × B

To be equal, A = 2 and B = 3

Therefore, A²B³

6 0
2 years ago
What is the mass of 1.6 mol of aluminum atom?
PIT_PIT [208]
Answer = 43.2

Because to find the mass you multiply the amount of moles ( 1.6) by the mass of the element ( mass of aluminium is 27) so
1.6 x 27 = 43.2g

Hope this helps
8 0
3 years ago
How many mL of 0.715 M HCl is required to neutralize 1.25 grams of sodium carbonate? (producing carbonic acid)
jonny [76]

Answer:

34 mL

Explanation:

We'll begin by calculating the number of mole in 1.25 g of sodium carbonate, Na₂CO₃. This can be obtained as follow:

Mass of Na₂CO₃ = 1.25 g

Molar mass of Na₂CO₃ = (23×2) + 12 + (16×3)

= 46 + 12 + 48

= 106 g/mol

Mole of Na₂CO₃ =?

Mole = mass /molar mass

Mole of Na₂CO₃ = 1.25 / 106

Mole of Na₂CO₃ = 0.012 mole

Next, we shall determine the number of mole HCl needed to react with 0.012 mole of Na₂CO₃.

The equation for the reaction is given below:

Na₂CO₃ + 2HCl —> H₂CO₃ + 2NaCl

From the balanced equation above,

1 mole of Na₂CO₃ reacted with 2 moles of HCl.

Therefore, 0.012 mole of Na₂CO₃ will react with = 0.012 × 2 = 0.024 mole of HCl.

Next, we shall determine the volume of HCl required for the reaction. This is illustrated:

Mole of HCl = 0.024 mole

Molarity of HCl = 0.715 M

Volume of HCl =?

Molarity = mole /Volume

0.715 = 0.024 / volume of HCl

Cross multiply

0.715 × volume of HCl = 0.024

Divide both side by 0.715

Volume of HCl = 0.024 / 0.715

Volume of HCl = 0.034 L

Finally, we shall convert 0.034 L to mL

This can be obtained as follow:

1 L = 1000 mL

Therefore,

0.034 L = 0.034 L × 1000 mL / 1 L

0.034 L = 34 mL

Therefore, 34 mL of HCl is needed for the reaction.

6 0
3 years ago
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