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lara [203]
3 years ago
10

A 2.61 g sample of a substance suspected of being pure gold is warmed to 72.8 ∘C and submerged into 15.8 g of water initially at

24.9 ∘C. The final temperature of the mixture is 26.1 ∘C. What is the specific heat capacity of the unknown substance (in J/g*ºC)?
Chemistry
1 answer:
Likurg_2 [28]3 years ago
5 0
 <span>mg = 2.42 g 
Tg = 72.2 deg.C 
mw = 15.8 g 
Tw = 24.5 
Tf = 27 deg. C 
Cw = 4.18 J/g. deg. C 

Energy balance for insulated system, 
ΔE = 0 
ΔUw + ΔUg = 0 
ΔUw = - ΔUg 
Qin = Qout 
mg*cg*ΔTg = mw*cw*ΔTw 
2.42*cg*(72.2 - 27) = 15.8*4.18*(27 - 24.5) 
cg = 1.5095 J/g. deg.C or 1.5095 J/g.K</span><span>
</span>
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In an experiment, two unknown compounds (one an alcohol and the other an ether) of equal molecular mass were dissolved in water.
-BARSIC- [3]

Answer: B. It is an ether because it is unable to to form a hydrogen bond, so it is less soluble than water

Explanation: Alcohols (ROH) are more soluble in water as they can form hydrogen bonding with water whereas ethers (ROR) are less soluble as they do not form hydrogen bonds with water.

For formation of hydrogen bond, the electronegative atom (F, Oand N) must be attached to hydrogen and in ethers (ROR), there is no hydrogen directly attached to electronegative oxygen atom, thus are less soluble in water.


4 0
3 years ago
Here is the electron configuration for Magnesium. How many total electrons are in the 2nd energy level?
balandron [24]

Answer:

8 electrons

Explanation:

Magnesium is present on group 2.

It has 2 valence electrons.

Electronic configuration of magnesium:

Mg₁₂ = 1s² 2s² 2p⁶ 3s²

1st energy level contain 2 electrons.(1s²)

2nd energy  level contain 8 electrons. (2s² 2p⁶)

3rd energy level contain 2 electrons. (3s²)

3rs energy level of magnesium is called valence shell. It contain two valance electrons. Magnesium can easily donate its two valance electrons and get stable electronic configuration.

It react with halogens and form salt. For example,

Mg + Cl₂   →   MgCl₂

7 0
3 years ago
Match each scientist to their discovery regarding the atom
neonofarm [45]

Answer:

Thomson--atoms cotain electron

Ernest Rutherford--atoms have a positive nucleus

R.A Millikan--electrons have Q=-1

Dalton--atoms are indivisible

3 0
3 years ago
Read 2 more answers
The dissociation of sulfurous acid (H2SO3) in aqueous solution occurs as follows:
aksik [14]

Answer:

The [SO₃²⁻]

Explanation:

From the first dissociation of sulfurous acid we have:

                         H₂SO₃(aq) ⇄ H⁺(aq) + HSO₃⁻(aq)

At equilibrium:  0.50M - x          x            x

The equilibrium constant (Ka₁) is:

K_{a1} = \frac{[H^{+}] [HSO_{3}^{-}]}{[H_{2}SO_{3}]} = \frac{x\cdot x}{0.5 - x} = \frac {x^{2}}{0.5 -x}

With Ka₁= 1.5x10⁻² and solving the quadratic equation, we get the following HSO₃⁻ and H⁺ concentrations:

[HSO_{3}^{-}] = [H^{+}] = 7.94 \cdot 10^{-2}M

Similarly, from the second dissociation of sulfurous acid we have:

                              HSO₃⁻(aq) ⇄ H⁺(aq) + SO₃²⁻(aq)

At equilibrium:  7.94x10⁻²M - x          x            x

The equilibrium constant (Ka₂) is:  

K_{a2} = \frac{[H^{+}] [SO_{3}^{2-}]}{[HSO_{3}^{-}]} = \frac{x^{2}}{7.94 \cdot 10^{-2} - x}  

Using Ka₂= 6.3x10⁻⁸ and solving the quadratic equation, we get the following SO₃⁻ and H⁺ concentrations:

[SO_{3}^{2-}] = [H^{+}] = 7.07 \cdot 10^{-5}M

Therefore, the final concentrations are:

[H₂SO₃] = 0.5M - 7.94x10⁻²M = 0.42M

[HSO₃⁻] = 7.94x10⁻²M - 7.07x10⁻⁵M = 7.93x10⁻²M

[SO₃²⁻] = 7.07x10⁻⁵M

[H⁺] = 7.94x10⁻²M + 7.07x10⁻⁵M = 7.95x10⁻²M

So, the lowest concentration at equilibrium is [SO₃²⁻] = 7.07x10⁻⁵M.

I hope it helps you!

8 0
3 years ago
Pls help me i dont know this
r-ruslan [8.4K]

Answer:

1. 12.6 moles

2. 8.95 moles

3.  2A + 5B → 3C

4. 48 moles

Explanation:

1. 2Fe + 3Cl₂ → 2FeCl₃

We assume the chlorine in excess. Ratio is 2:2

2 moles of Fe, can produce 2 moles of chloride

12.6 moles of Fe will produce 12.6 moles of chloride.

2. 2Fe + 3Cl₂ → 2FeCl₃

For the same reaction, first of all we need to convert the mass to moles:

500 g . 1mol / 55.85 g = 8.95 mol

As ratio is 2:2, the moles we have are the same, that the produced

4. The reaction for the combustion is:

2C₂H₆ (g) + 7O₂ (g) → 4CO₂ (g) + 6H₂O (l)

We assume the oxygen in excess.

Ratio is 2:6, so 2 mol of ethane produce 6 moles of water

Therefore 16 moles of ethane may produce (16 .6) / 2 = 48 moles

3 0
3 years ago
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