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3 years ago

Review energy changes by identifying the correct statements about each reaction.

Chemistry

1 answer:

Grace [21]3 years ago

5 0

Answer: The reaction is exothermic

The $\Delta H$ value is negative.

Heat is a product.

Explanation:

$2H_2(g)+O_2(g)\rightarrow 2H_2O(l)+136.6kcal$

Endothermic reactions are defined as the reactions in which energy of the product is greater than the energy of the reactants. The total energy is absorbed in the form of heat and $\Delta H$ for the reaction comes out to be positive.

Exothermic reactions are defined as the reactions in which energy of the product is lesser than the energy of the reactants. The total energy is released in the form of heat and $\Delta H$ for the reaction comes out to be negative.

The substances which are written on the left side of the arrow are reactants and the substances which are written on the right side of the arrow are products. Thus heat is a product.

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Convert 4.5 X 1022 molecules of H2O to moles.

noname [10]

Answer:

<h3>The answer is 0.075 moles</h3>

Explanation:

To find the number of moles in a substance given it's number of entities we use the formula

$n = \frac{N}{L} \\$

where n is the number of moles

N is the number of entities

L is the Avogadro's constant which is

6.02 × 10²³ entities

From the question we have

$n = \frac{4.5 \times {10}^{22} }{6.02 \times {10}^{23} } \\ = 0.074750830...$

We have the final answer as

<h3>0.075 moles</h3>

Hope this helps you

3 0

2 years ago

During a combustion reaction, 9.00 grams of oxygen reacted with 3.00 grams of CH4.

Monica [59]

Answer:

0.74 grams of methane

Explanation:

The balanced equation of the combustion reaction of methane with oxygen is:

CH₄ + 2 O₂ → CO₂ + 2 H₂O

it is clear that 1 mol of CH₄ reacts with 2 mol of O₂.

firstly, we need to calculate the number of moles of both

for CH₄:

number of moles = mass / molar mass = (3.00 g) / (16.00 g/mol) = 0.1875 mol.

for O₂:

number of moles = mass / molar mass = (9.00 g) / (32.00 g/mol) = 0.2812 mol.

it is clear that O₂ is the limiting reactant and methane will leftover.

using cross multiplication

1 mol of CH₄ needs → 2 mol of O₂

??? mol of CH₄ needs → 0.2812 mol of O₂

∴ the number of mol of CH₄ needed = (0.2812 * 1) / 2 = 0.1406 mol

so 0.14 mol will react and the remaining CH₄

mol of CH₄ left over = 0.1875 -0.1406 = 0.0469 mol

now we convert moles into grams

mass of CH₄ left over = no. of mol of CH₄ left over * molar mass

= 0.0469 mol * 16 g/mol = 0.7504 g

So, the right choice is 0.74 grams of methane

3 0

3 years ago

You are burning wood to heat water for your industrial process. What is the mass of wood required to raise the temperature of 10

natta225 [31]

Answer:

18,8kg of wood

Explanation:

The energy you need to to raise the temperature of 1000 kg of water from 25.0 to 100.0 °C is:

q = C×m×ΔT

Where: q is heat, C is specific heat of water (4,184J/g°C), m is mass in grams (1000x10³g), and ΔT is 100,0°C - 25,0°C = 75,0°C

Replacing:

q = 4,184J/g°C×1000x10³g×75,0°C

<u><em>q = 3,14x10⁸ J of heat are required</em></u>

Now, if the heating value of dry wood is 16,72 MJ/kg = 16,72x10⁶ J/kg, mass of wood required is:

3,14x10⁸J × (1kg / 16,72x10⁶ J) = <em>18,8 kg of wood are required</em>

I hope it helps!

5 0

3 years ago

80. Calculate AHıxn for the reaction:<br><br> CaO(s) + CO2(g) → CaCO3().

ioda

Still chill still chill still chill

6 0

3 years ago

2 bromocyclopentanamine structural formula

Elis [28]

Answer:

The structure is given in attached file.

Explanation:

Explanation

2-bromocyclopentamine (Figure attached) is a synthetic compound which is synthesized by substitution reaction of cyclopentamine and hydrobromide. Its molecular formula and molecular mass are C5H10NBr and 164.05 mol/g respectively. It is a very reactive compound so it doesn’t available in pure form, it is present in market as a mixture of 2-bromocyclopentamine and Hydrobromide.

Properties :

Its boiling point is 115 0C

Its melting point is – 75 oC

It is highly flammable

It is highly toxic

It is irritant

It is corrosive in nature

5 0

3 years ago