Chemistry
Chemistry
4th Edition
ISBN: 9780393919370
Author: Thomas R. Gilbert
Publisher: NORTON
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Chapter 5, Problem 5.69QP

(a)

Interpretation Introduction

Interpretation: The addition of 2.00g of Mg metal in 95.0mL of 1.00M of HCl in a coffee-cup calorimeter raised the temperature by 9.2°C . The balanced net ionic equation of the reaction is to be written and ΔHrxn is to be calculated.

Concept introduction: The heat of reaction or enthalpy of the reaction (ΔHrxn) is defined as the amount of energy released or absorbed during formation of product. It is calculated by formula,

q=n×cp×ΔT

To determine: The balanced net ionic equation of the reaction.

(a)

Expert Solution
Check Mark

Answer to Problem 5.69QP

Solution

The net ionic equation is,

Mg(s)+2H+(aq)Mg2+(aq)+H2(g)

Explanation of Solution

Explanation

The balanced chemical equation is given as,

Mg(s)+2HCl(aq)MgCl2(aq)+H2(g)

The total ionic equation is given as,

Mg(s)+2H+(aq)+2Cl(aq)Mg2+(aq)+2Cl(aq)+H2(g)

The net ionic equation is,

Mg(s)+2H+(aq)Mg2+(aq)+H2(g)

(b)

Interpretation Introduction

To determine: The enthalpy of the reaction ΔHrxn .

(b)

Expert Solution
Check Mark

Answer to Problem 5.69QP

Solution

The ΔHrxn of the reaction is 2808.4J/mol_ .

Explanation of Solution

Explanation

The amount of Mg metal added is 2.00g .

The volume of HCl is 95.0mL .

The molarity of HCl is 1.00M .

Temperature change of the reaction 9.2°C .

The molar heat capacity of 1.00M HCl is 75.3J/mol°C .

The total number of moles of Mg are calculated by the formula,

nMg=mM1

Where,

  • m is the given mass of Mg .
  • M1 is the molar mass of Mg .

The molar mass of Mg is 24.3g/mol .

Substitute the molar mass and given mass of Mg in the above formula,

nMg=2g24.3g/mol=0.082mol

The total number of moles of 1.00M HCl are calculated by formula,

nHCl=M×V

Where,

  • M is the molarity of HCl .
  • V is the volume of HCl .

Convert 95.0mL into L .

95.0mL=95.01000L=0.095L

Substitute the molarity and volume of HCl in the above formula,

nHCl=1.00M×0.095L=0.095mol

The balanced chemical equation is given as,

Mg(s)+2HCl(aq)MgCl2(aq)+H2(g)

The above equation shows that 1mol if Mg reacted with 2mol of HCl .

The number of moles of Mg react with 0.095mol of HCl is calculated by,

NMg=nHCl2

Substitute the number of moles of HCl .

NMg=0.095mol2=0.0475mol

The amount of heat absorbed or released is calculated by formula,

q=mHCl×c×ΔT (1)

Where,

  • mHCl is the mass of HCl reacted with Mg .
  • C is the specific heat capacity of HCl .
  • ΔT is the temperature change.

The mass of the HCl is calculated by formula,

mHCl=nHCl×M2

Where,

  • M2 is the molar mass of HCl .

The molar mass of HCl is =H+Cl=1g/mol+35.5g/mol=36.5g/mol

Substitute the values of molar mass and number of moles of HCl in the above formula,

mHCl=0.095mol×36.5g/mol=3.46g

The specific heat capacity is calculated by formula

c=cpM3

Where,

  • Cp is the given molar heat capacity.
  • M3 is the molar mass of water.

The molar mass of water is =2H+O=2×1g/mol+1×16g/mol=18g/mol

Substitute the values of molar heat capacity and molar mass of water in above formula.

c=75.3J/mol°C×18g/mol=4.183J/g°C

Substitute the values of specific heat capacity, mass of HCl and change in temperature in equation (1).

q=3.467g×4.183J/g°C×9.2°C=133.4J

The ΔHrxn of the reaction is calculated by formula,

ΔHrxn=qNMg

Substitute the values of heat absorbed and number of moles of Mg .

ΔHrxn=133.4J0.0475mol=2808.4J/mol_

Therefore, the ΔHrxn of the reaction is 2808.4J/mol_ .

Conclusion

  1. a. The net ionic equation is,

Mg(s)+2H+(aq)Mg2+(aq)+H2(g)

  1. b. The ΔHrxn of the reaction is 2808.4J/mol_

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Chapter 5 Solutions

Chemistry

Ch. 5.5 - Prob. 11PECh. 5.6 - Prob. 12PECh. 5.6 - Prob. 13PECh. 5.7 - Prob. 14PECh. 5.7 - Prob. 15PECh. 5.7 - Prob. 16PECh. 5.8 - Prob. 17PECh. 5 - Prob. 5.1VPCh. 5 - Prob. 5.2VPCh. 5 - Prob. 5.3VPCh. 5 - Prob. 5.4VPCh. 5 - Prob. 5.5VPCh. 5 - Prob. 5.6VPCh. 5 - Prob. 5.7VPCh. 5 - Prob. 5.8VPCh. 5 - Prob. 5.9QPCh. 5 - Prob. 5.10QPCh. 5 - Prob. 5.11QPCh. 5 - Prob. 5.12QPCh. 5 - Prob. 5.13QPCh. 5 - Prob. 5.14QPCh. 5 - Prob. 5.15QPCh. 5 - Prob. 5.16QPCh. 5 - Prob. 5.17QPCh. 5 - Prob. 5.18QPCh. 5 - Prob. 5.19QPCh. 5 - Prob. 5.20QPCh. 5 - Prob. 5.21QPCh. 5 - Prob. 5.22QPCh. 5 - Prob. 5.23QPCh. 5 - Prob. 5.24QPCh. 5 - Prob. 5.25QPCh. 5 - Prob. 5.26QPCh. 5 - Prob. 5.27QPCh. 5 - Prob. 5.28QPCh. 5 - Prob. 5.29QPCh. 5 - Prob. 5.30QPCh. 5 - Prob. 5.31QPCh. 5 - Prob. 5.32QPCh. 5 - Prob. 5.33QPCh. 5 - Prob. 5.34QPCh. 5 - Prob. 5.35QPCh. 5 - Prob. 5.36QPCh. 5 - Prob. 5.37QPCh. 5 - Prob. 5.38QPCh. 5 - Prob. 5.39QPCh. 5 - Prob. 5.40QPCh. 5 - Prob. 5.41QPCh. 5 - Prob. 5.42QPCh. 5 - Prob. 5.43QPCh. 5 - Prob. 5.44QPCh. 5 - Prob. 5.45QPCh. 5 - Prob. 5.46QPCh. 5 - Prob. 5.47QPCh. 5 - Prob. 5.48QPCh. 5 - Prob. 5.49QPCh. 5 - Prob. 5.50QPCh. 5 - Prob. 5.51QPCh. 5 - Prob. 5.52QPCh. 5 - Prob. 5.53QPCh. 5 - Prob. 5.54QPCh. 5 - Prob. 5.55QPCh. 5 - Prob. 5.56QPCh. 5 - Prob. 5.57QPCh. 5 - Prob. 5.58QPCh. 5 - Prob. 5.59QPCh. 5 - Prob. 5.60QPCh. 5 - Prob. 5.61QPCh. 5 - Prob. 5.62QPCh. 5 - Prob. 5.65QPCh. 5 - Prob. 5.66QPCh. 5 - Prob. 5.67QPCh. 5 - Prob. 5.68QPCh. 5 - Prob. 5.69QPCh. 5 - Prob. 5.70QPCh. 5 - Prob. 5.71QPCh. 5 - Prob. 5.72QPCh. 5 - Prob. 5.73QPCh. 5 - Prob. 5.74QPCh. 5 - Prob. 5.75QPCh. 5 - Prob. 5.76QPCh. 5 - Prob. 5.77QPCh. 5 - Prob. 5.78QPCh. 5 - Prob. 5.79QPCh. 5 - Prob. 5.80QPCh. 5 - Prob. 5.81QPCh. 5 - Prob. 5.82QPCh. 5 - Prob. 5.83QPCh. 5 - Prob. 5.84QPCh. 5 - Prob. 5.85QPCh. 5 - Prob. 5.86QPCh. 5 - Prob. 5.87QPCh. 5 - Prob. 5.88QPCh. 5 - Prob. 5.89QPCh. 5 - Prob. 5.90QPCh. 5 - Prob. 5.91QPCh. 5 - Prob. 5.92QPCh. 5 - Prob. 5.93QPCh. 5 - Prob. 5.94QPCh. 5 - Prob. 5.95QPCh. 5 - Prob. 5.96QPCh. 5 - Prob. 5.97QPCh. 5 - Prob. 5.98QPCh. 5 - Prob. 5.99QPCh. 5 - Prob. 5.100QPCh. 5 - Prob. 5.101QPCh. 5 - Prob. 5.102QPCh. 5 - Prob. 5.103APCh. 5 - Prob. 5.104APCh. 5 - Prob. 5.105APCh. 5 - Prob. 5.106APCh. 5 - Prob. 5.107APCh. 5 - Prob. 5.108APCh. 5 - Prob. 5.109APCh. 5 - Prob. 5.110APCh. 5 - Prob. 5.111APCh. 5 - Prob. 5.112APCh. 5 - Prob. 5.113APCh. 5 - Prob. 5.114APCh. 5 - Prob. 5.115APCh. 5 - Prob. 5.116APCh. 5 - Prob. 5.117APCh. 5 - Prob. 5.118APCh. 5 - Prob. 5.119APCh. 5 - Prob. 5.120APCh. 5 - Prob. 5.121APCh. 5 - Prob. 5.122APCh. 5 - Prob. 5.123APCh. 5 - Prob. 5.124APCh. 5 - Prob. 5.125APCh. 5 - Prob. 5.126APCh. 5 - Prob. 5.127APCh. 5 - Prob. 5.128APCh. 5 - Prob. 5.129APCh. 5 - Prob. 5.130APCh. 5 - Prob. 5.131APCh. 5 - Prob. 5.132APCh. 5 - Prob. 5.133APCh. 5 - Prob. 5.134APCh. 5 - Prob. 5.135APCh. 5 - Prob. 5.136APCh. 5 - Prob. 5.137APCh. 5 - Prob. 5.138APCh. 5 - Prob. 5.139APCh. 5 - Prob. 5.140APCh. 5 - Prob. 5.141APCh. 5 - Prob. 5.142APCh. 5 - Prob. 5.143AP
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