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3 years ago

A sample has 25.7g of calcium oxide. How many moles are CaO are contained in the sample?

Chemistry

2 answers:

Arturiano [62]3 years ago

7 0

Here is the working out:

Mass= mr x mol
Mol = mass/mr
So molCao = 25.7/(16+40)= 0.459moles

Hope this helps!!! Xx

Fantom [35]3 years ago

3 0

0.4582951420714879 moles

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The labels have fallen off three bottles containing powdered samples of metals; one contains zinc, one lead, and the other plati

Alinara [238K]

Here we have to identify the metal powder by the given disposal.

The identification of Zinc can be done by 1 m nitric acid (HNO₃) and Ni(NO₃)₂ which will produce hydrogen gas by reaction and displacement reaction as shown below.

Zn + 2 HNO₃ = Zn(NO₃)₂ + H₂ (g)

Zn + Ni(NO₃)₂ = Zn(NO₃)₂ + Ni

The identification of lead can be done by the reaction with 1 m nitric acid (HNO₃) which produces lead nitrate.

The reaction is-

Pb + 4HNO₃ = Pb(NO₃)₂ + 2NO₂ + 2H₂O

The identification of platinum can be done by the reaction with all the given disposal as it will not react with any of the compound.

1. Identification of Zinc (Zn):

(a) Zn metal will not react with sodium nitrate (NaNO₃) as sodium remains at the lower position of the activity series than zinc.

Zn + NaNO₃ = No reaction

(b) Zn metal will react with 1 m HNO₃ to form hydrogen gas. The reaction is:

Zn + 2 HNO₃ = Zn(NO₃)₂ + H₂ (g)

(c) Zn will react with nickel nitrate [Ni(NO₃)₂] because it may only cause displacement reaction the reduction potential of Zn²⁺/Zn (-0.76) is less than that of Ni²⁺/Ni (-0.23). Thus the reaction will be:

Zn + Ni(NO₃)₂ = Zn(NO₃)₂ + Ni

2. Identification of lead (Pb):

(a) Pb metal will not react with sodium nitrate (NaNO₃) as sodium remains at the lower position of the activity series than Pb.

Pb + NaNO₃ = No reaction

(b) Pb reacts with HNO₃ to form lead nitrate. The reaction is:

Pb + 4HNO₃ = Pb(NO₃)₂ + 2NO₂ + 2H₂O

(c) The standard reduction potential of Pb²⁺/Pb is more than nickel Ni²⁺/Ni thus there will be no reaction between Pb and NI(NO₃)₂.

Pb + Ni(NO₃)₂ = No reaction.

3. Identification of platinum (Pt)

(a) Pt metal will not react with sodium nitrate (NaNO₃) as sodium remains at the lower position of the activity series than Pt.

Pt + NaNO₃ = No reaction.

(b) The standard reduction potential of Pt²⁺/Pt is so high (+1.188) thus there will be no reaction with HNO₃.

Pt + HNO₃ = No reaction

(c) The standard reduction potential of Pt²⁺/Pt is more than nickel Ni²⁺/Ni thus there will be no reaction between Pt and Ni(NO₃)₂.

Pt + Ni(NO₃)₂ = No reaction.

8 0

3 years ago

A hot lump of 39.9 g of iron at an initial temperature of 78.1 °C is placed in 50.0 mL H 2 O initially at 25.0 °C and allowed to

Drupady [299]

Answer : The final temperature of the mixture is $29.6^oC$

Explanation :

In this problem we assumed that heat given by the hot body is equal to the heat taken by the cold body.

$q_1=-q_2$

$m_1\times c_1\times (T_f-T_1)=-m_2\times c_2\times (T_f-T_2)$

where,

$c_1$ = specific heat of iron = $0.499J/g^oC$

$c_2$ = specific heat of water = $4.18J/g^oC$

$m_1$ = mass of iron = 39.9 g

$m_2$ = mass of water = $Density\times Volume=1g/mL\times 50.0mL=50.0g$

$T_f$ = final temperature of mixture = ?

$T_1$ = initial temperature of iron = $78.1^oC$

$T_2$ = initial temperature of water = $25.0^oC$

Now put all the given values in the above formula, we get

$(39.9g)\times (0.499J/g^oC)\times (T_f-78.1)^oC=-(50.0g)\times 4.18J/g^oC\times (T_f-25.0)^oC$

$T_f=29.6^oC$

Therefore, the final temperature of the mixture is $29.6^oC$

8 0

3 years ago

Use the reaction 1₂(s) = 12(g), AH = 62.4 kJ/mol, AS = 0.145 kJ/(mol-K), for

Sati [7]

The Reaction is spontaneous when temperature is 430 K. Hence, Option (C) is correct.

<h3></h3><h3>What is Spontaneous reaction ?</h3>

Reactions are favorable when they result in a decrease in enthalpy and an increase in entropy of the system.

When both of these conditions are met, the reaction occurs naturally.

Spontaneous reaction is a reaction that favors the formation of products at the conditions under which the reaction is occurring.

According to Gibb's equation:

ΔG = ΔH - TΔS

ΔG = Gibbs free energy

ΔH = enthalpy change = +62.4 kJ/mol

ΔS = entropy change = +0.145 kJ/molK

T = temperature in Kelvin

ΔG = +ve, reaction is non spontaneous
ΔG = -ve, reaction is spontaneous
ΔG = 0, reaction is in equilibrium

ΔH - TΔS = 0 for reaction to be spontaneous

T = ΔH / ΔS

Here,

T = 500K

Thus the Reaction is spontaneous when temperature is 500 K.

Learn more about Gibbs free energy here ;

https://brainly.in/question/13372282

#SPJ1

3 0

2 years ago

How do waves affect matter they are traveling through?

s344n2d4d5 [400]

The energy of the wave does not move through anything

4 0

3 years ago

What is the total number of moles represented by 20 grams of CACO3

Nutka1998 [239]

Answer:

B. 0.2.

Explanation:

We can use the relation:

<em>n = mass/molar mass</em>

mass of CaCO₃ = 20 g, molar mass of CaCO₃ = 100.0869 g/mol.

<em>∴ n = mass/molar mass = </em>(20 g)/(100.0869 g/mol) <em>= 0.1998 ≅ 0.2 mol.</em>

<em>So, the right choice is: B. 0.2.</em>

8 0

3 years ago