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lubasha
28 days ago
7

A pan containing 20.0 grams of water was allowed to cool from a temperature of 95.0 °C. If the amount of heat released is 1,200

joules, what is the approximate final temperature of the water? 75 °C 78 °C 81 °C 87 °C
Chemistry
1 answer:
castortr0y [2.9K]28 days ago
7 0

Answer:

81°C.

Justification:

We can arrive at this conclusion using the formula:

Q = m.c.ΔT,

where Q denotes the heat lost by water (Q = - 1200 J).

m represents the mass of water (m = 20.0 g).

c indicates the specific heat of water (c = 4.186 J/g.°C).

ΔT signifies the difference between the starting temperature and the final temperature (ΔT = final T - initial T = final T - 95.0°C).

Given Q = m.c.ΔT

It follows that (- 1200 J) = (20.0 g)(4.186 J/g.°C)(final T - 95.0°C ).

(- 1200 J) = 83.72 final T - 7953.

∴ final T = (- 1200 J + 7953)/83.72 = 80.67°C ≅ 81.0°C.

Consequently, the correct answer is: 81°C.

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The balanced chemical equation for the neutralization of HCl with NaHCO_{3} is:

HCl (aq) + NaHCO_{3}(aq)--> NaCl (aq) + H_{2}O(l)+CO_{2} (g)

Given weight of NaHCO_{3} = 5g

Moles of NaHCO_{3} = 5 g *\frac{1 mol}{84 g} = 0.05952 mol NaHCO_{3}

Volume of HCl solution = 50 cm^{3} * \frac{1 mL}{1cm^{3}} = 50 mL

Assuming the density of the solution is 1.0 g/mL

Mass of HCl solution = 50 g

Overall mass of the solution = 50 g + 5 g = 55 g

To find the heat of neutralization, we calculate:

Q = m C ΔT

where m equals the mass of the solution = 55 g

C represents the specific heat capacity of the solution = 4.184\frac{J}{g. ^{0}C}

ΔT signifies the temperature change = 6.8 K = (6.8 - 273) C = -266.2^{0}C

Q = 55 g * 4.184 \frac{J}{g. K}(6.8K) = 1565 J

The enthalpy of neutralization per mole of NaHCO_{3}

= \frac{1565J}{0.05952 mol} = 26294 \frac{J}{mol}*\frac{1 kJ}{1000J} =26.294kJ/mol

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1 month ago
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For which applications would you choose a liquid over a gas or solid?
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Solution:

Washing Clothes & Dissolving Sugar

Clarification:

Consider each scenario:

1) For washing clothes, water is essential; without it, washing is ineffective.

2) Connecting brake pedals to brake pads requires solids, not liquids.

3) To deodorize a space, one would likely reach for an aerosol spray, which is a gas.

4) Sculpting involves solid tools and a solid medium.

5) Dissolving sugar necessitates a liquid to be effective!

6) While one might assert that paint is a liquid, it still might not fit the category; I would categorize this application as solid.

7) Gears employed in machinery are solid components!

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For which of the following reactions is ΔHrxn equal to ΔHf of the product? You do not need to look up any values to answer this
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Answer:

In all listed reactions, ΔH°rxn does not correspond to the ΔH°f of the resulting product.

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The standard enthalpy of formation (ΔH°f) signifies the enthalpy change that occurs when 1 mole of a product is created from its basic elements in their standard states.

1/2 O₂(g) + H₂O(g) ⟶ H₂O₂(g)

ΔH°rxn does not equal ΔH°f of the product, since H₂O(g) is a compound rather than an element.

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ΔH°rxn is not the same as ΔH°f of the product because Na and F are not in their standard states (Na(s); F₂(g)).

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