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dimaraw [331]
3 years ago
6

How many molecules of ethanol (c2h5oh) (the alcohol in alcoholic beverages) are present in 155 ml of ethanol? the density of eth

anol is 0.789 g/cm3?
Chemistry
1 answer:
ozzi3 years ago
4 0

First convert volume to mass:

mass = 0.789 g/mL * 155 mL = 122.295 g

 

Then convert mass to number of moles:

number of moles = 122.295 g * (1 mole / 46 g) = 2.66 moles

 

Using avogadros number, we get the molecules:

<span>number of molecules = 2.66 moles * 6.022 x 10^23 molecules / mole = 1.6 x 10^24 molecules</span>

You might be interested in
Is volcanoes eruption rapid change or slow change​
irakobra [83]

Answer:

Fast change

Explanation:

Weathering, erosion, and deposition are examples of slow change. Earthquakes, erupting volcanoes, and landslides happen fast. Therefore, they can change the Earth's surface very quickly.

3 0
3 years ago
A chemist measures the enthalpy change ?H during the following reaction: Fe (s) + 2HCl (g) ? FeCl2 (s) + H2 (g) =?H?157.kJ Use t
erik [133]

Correct Question:

A chemist measures the enthalpy change ΔH during the following reaction: Fe(s) + 2HCl(g)-->FeCl2(s) + H2 ΔH=-157.0 kJ. Use this information to complete the table below. Round each of your answers to the nearest kJ/mol

Answer:

-314 kJ

+628 kJ

+157 kJ

Explanation:

The enthalpy change of a reaction measures the amount of heat that is lost or gained by it. If ΔH >0 the heat is gained, and the reaction is called endothermic, if ΔH<0, the heat is lost, and the reaction is called exothermic.

If the reaction is inverted, the value of ΔH is inverted too (the opposite endothermic reaction is exothermic), and if the reaction is multiplied by a constant, ΔH will be multiplied by it too.

1) 2Fe(s) + 4HCl --> 2FeCl2(s) + 2H2(g)

This reaction is the product of the given reaction by 2, so

ΔH = 2*(-157) = -314 kJ

2) 4FeCl2(s) + 4H2(g) --> 4Fe(s) + 8HCl(g)

This reaction is the inverted reaction given multiplied by 4, so

ΔH = 4*(157) = +628 kJ

3) FeCl2(s) + H2(g) --> Fe(s) + 2HCl

This reaction is the inverted reaction given, so

ΔH = +157 kJ

4 0
3 years ago
Zn + I2 ---&gt; Znl2<br> Determine the theoretical yield of the product if 2g of Zn is used
egoroff_w [7]

Answer:

Mass = 9.58 g

Explanation:

Given data:

Mass of Zn = 2g

Theoretical yield of ZnI₂ = ?

Solution:

Chemical equation:

Zn + I₂       →     ZnI₂

Number of moles of Zn:

Number of moles = mass/molar mass

Number of moles = 2g / 65.38 g/mol

Number of moles = 0.03 mol

Now we will compare the moles of Zn and ZnI₂.

                   Zn           :          ZnI₂

                    1             :           1

                  0.03        :         0.03

Mass of ZnI₂:

Mass = number of moles × molar mass

Mass = 0.03 mol × 319.22 g/mol

Mass = 9.58 g

4 0
3 years ago
Consider the reaction directly below and answer parts a and b. C6H4(OH)2 (l) + H2O2 (l) à C6H4O2 (l) + 2 H2O (l)
dedylja [7]

Answer:

a. -206,4kJ

b. Surroundings will gain heat.

c. -115kJ are given off.

Explanation:

It is possible to obtain ΔH of a reaction using Hess's law that consist in sum the different ΔH's of other reactions until obtain the reaction you need.

Using:

<em>(1) </em>C₆H₄(OH)₂(l) → C₆H₄O₂(l) + H₂(g) ΔH: +177.4 kJ

<em>(2) </em>H₂(g) + O₂(g) → H₂O₂ (l) ΔH: -187.8 kJ

<em>(3) </em>H₂(g) + 1/2O₂(g) → H₂O(l) ΔH: -285.8 kJ

It is possible to obtain:

C₆H₄(OH)₂(l) + H₂O₂(l) → C₆H₄O₂(l) + 2H₂O(l)

From (1)-(2)+2×(3). That is:

<em>(1) </em>C₆H₄(OH)₂(l) → C₆H₄O₂(l) + H₂(g) ΔH: +177.4 kJ

<em>-(2) </em>H₂O₂(l) → H₂(g) + O₂(g) ΔH: +187.8 kJ

<em>2x(3) </em>2H₂(g) + O₂(g) → 2H₂O(l) ΔH: 2×-285.8 kJ

The ΔH you obtain is:

+177,4kJ + 187,8kJ - 2×285.8 kJ =<em> -206,4kJ</em>

b. When ΔH of a reaction is <0, the reaction is exothermic, that means that the reaction produce heat and the <em>surroundings will gain this heat.</em>

c. 20,0g of H₂O are:

20,0g×\frac{1mol}{18,01g} = <em>1,11 mol H₂O</em>

As 2 moles of H₂O are produced when -206,4kJ are given off, when 1,11mol of H₂O are produced, there are given off:

1,11mol H₂O×\frac{-206,4kJ}{2mol} =<em> -115kJ</em>

I hope it helps!

8 0
3 years ago
What is an indicator that a chemical change has occurred?
Aleks04 [339]

Answer:

That something has changed chemically

Explanation:

Uh...Google it

6 0
3 years ago
Read 2 more answers
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