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andreev551 [17]
3 years ago
5

2. How many grams of water can be heated from 20.0 oC to 75oC using 12500.0 Joules?

Chemistry
2 answers:
Katyanochek1 [597]3 years ago
8 0
Q=12500.0 J
t₁=20.0°C
t₂=75°C
c=4200 J/(kg·°C)

Q=cm(t₂-t₁)
m=Q/{c(t₂-t₁)}

m=12500.0/{4200(75-20)}=0.0541 kg = 54.1 g
kenny6666 [7]3 years ago
4 0

Answer;

  = 0.054 kg or 54 g

Explanation;

Using the equation; Q = mcΔT where Q is the quantity of heat transferred, m is the mass, c is specific heat of the substance, ΔT is delta T, the change in temperature.  

ΔT = 75 - 20 = 55 C.  

Solve the equation for m  

m = Q/ cΔT

Mass = 12500 / (55 × 4200)

        = 0.054 kg or 54 g


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2 nf3 + 225 kj -> n2 + 3f2 is it exothermic or endothermic
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3 years ago
What is the Net Ionic equation for this chemical reaction: FeBr2+Na2S=FeS+2NaBr​
Artyom0805 [142]

Answer: Fe<em>(aq)</em>+S<em>(aq)</em>=FeS<em>(s)</em>

Explanation: The Sodium and Bromine are spectator ions because they don't react with anything, you can see this by writing the ionic equation like so:

1.) Molecular formula (given): FeBr2 (aq)+Na2S (aq)= FeS(s)+2NaBr(aq)

Each dissolved FeBr2 breaks up into one Fe with a charge of 2+ and two Br with a negative charge. This gives you:

Fe(aq)+ 2Br(aq)+Na2S(aq)=FeS(s)+2NaBr

2.) Now repeat what was shown with the other compounds in the given molecular formula, and pay attention to the states that each ion is in (solid, liquid, aqueous, gas) because this will give you the ionic equation, which from there you can get rid of any ions that don't change amount or state.

3.) Ionic formula: Fe(aq)+ <u>2Br(aq)</u>+<u>2 Na(aq)</u>+S (aq)=FeS(s)+<u>2 Na(aq)+2Br(aq)</u>

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Hope this helps :)

7 0
3 years ago
Calculate the change in pH when 71.0 mL of a 0.760 M solution of NaOH is added to 1.00 L of a solution that is 1.0O M in sodium
Eddi Din [679]

Explanation:

It is known that pK_{a} value of acetic acid is 4.74. And, relation between pH and pK_{a} is as follows.

                    pH = pK_{a} + log \frac{[CH_{3}COOH]}{[CH_{3}COONa]}

                          = 4.74 + log \frac{1.00}{1.00}

So, number of moles of NaOH = Volume × Molarity

                                                   = 71.0 ml × 0.760 M

                                                    = 0.05396 mol

Also, moles of  CH_{3}COOH = moles of CH_{3}COONa

                                          = Molarity × Volume

                                          = 1.00 M × 1.00 L

                                          = 1.00 mol

Hence, addition of sodium acetate in NaOH will lead to the formation of acetic acid as follows.

            CH_{3}COONa + NaOH \rightarrow CH_{3}COOH

Initial :    1.00 mol                                  1.00 mol

NaoH addition:               0.05396 mol

Equilibrium : (1 - 0.05396 mol)    0           (1.00 + 0.05396 mol)

                    = 0.94604 mol                       = 1.05396 mol

As, pH = pK_{a} + log \frac{[CH_{3}COONa]}{[CH_{3}COOH]}

               = 4.74 +  log \frac{0.94604}{1.05396}

               = 4.69

Therefore, change in pH will be calculated as follows.

                         pH = 4.74 - 4.69

                               = 0.05

Thus, we can conclude that change in pH of the given solution is 0.05.

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A small portion of a crystal lattice is sketched below. What is the name of the unit cell of this lattice? Your answer must be a
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This is an incomplete question, the given sketch is shown below.

Answer : The name of given unit cell is, FCC (face-centered cubic unit cell)

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Unit cell : It is defined as the smallest 3-dimensional portion of a complete space lattice which when repeated over the and again in different directions produces the complete space lattice.

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In SCC, the atoms are arranged at the corners.

Z=\frac{1}{8}\times 8=1

The number of atoms of unit cell = Z = 1

In BCC, the atoms are arranged at the corners and the body center.

Z=\frac{1}{8}\times 8+1=2

The number of atoms of unit cell = Z = 2

The given unit cell is, FCC because the atoms are arranged at the corners and the center of the 6 faces.

Z=\frac{1}{8}\times 8+\frac{1}{2}\times 6=4

The number of atoms of unit cell = Z = 4

Thus, the name of given unit cell is, FCC (face-centered cubic unit cell)

7 0
3 years ago
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