Chapter 10, Problem 99IL

### Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
ISBN: 9781337399074

Chapter
Section

### Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
ISBN: 9781337399074
Textbook Problem

# One way to synthesize diborane, B2H6, is the reaction2 NaBH4(s) + 2 H3PO4(ℓ) → B2H6(g) + 2 NaH2PO4(s) + 2 H2(g) (a) If you have 0.136 g of NaBH4 and excess H3PO4, and you collect the resulting B2H6 in a 2.75-L flask at 25 °C, what is the pressure of the B2H6 in the flask? (b) A by-product of the reaction is H2 gas. If both B2H6 and H2 gas come from this reaction, what is the total pressure in the 2.75-L flask (after reaction of 0.136 g of NaBH4 with excess H3PO4) at 25 °C?

(a)

Interpretation Introduction

Interpretation:

For the given reaction the pressure of the given gas under given conditions and the total pressure under given conditions should be determined.

Concept Introduction:

Balanced Chemical Equation:

The chemical reaction when the number of atoms present in the reactant side of the reaction should be equal to the number and the charge of atoms present in the product side of the reaction which then only be considered as balanced.

Ideal gas equation:

Any gas is described by using four terms namely pressure, volume, temperature and the amount of gas. Thus combining three laws namely Boyle’s, Charles’s Law and Avogadro’s Hypothesis the following equation could be obtained. It is referred as ideal gas equation.

nTPV = RnTPPV = nRTwhere,n = moles of gasP = pressureT = temperatureR = gas constant

Under some conditions gases don not behave like ideal gas that is they deviate from their ideal gas properties. At lower temperature and at high pressures the gas tends to deviate and behave like real gases.

Boyle’s Law:

At given constant temperature conditions the mass of given ideal gas in inversely proportional to its volume.

Charles’s Law:

At given constant pressure conditions the volume of ideal gas is directly proportional to the absolute temperature.

Two equal volumes of gases with same temperature and pressure conditions tend to have same number of molecules with it.

Mole fraction: The mole fraction of denotes the individual presence of the component present in the given chemical reaction.

Consider general equation that contains reactants X and Y then the mole fraction of X is determined as follows,

Mole fraction of Mole fraction of one component = Moles of that componentTotal moles present in the reactionMole fraction of X = Number of moles of XNumber of moles of X + Number of moles of Y

The relationship between partial pressure and Ptotal is

Pi=χiPtotalwhere,Pi=partial pressureχi=molefractionPtotal=Totalpressure

Explanation

It is given that there is excess of H3PO4 and hence NaBH4 acts as limiting agent which the product formation is purely based on the limiting reagent.

Consider the given chemical reaction and calculate the pressure of B2H6(g) as follows,

â€‚Â PÂ =nRTVâ€Šâ€Š=â€Šâ€Š4.917Ã—10-3Ã—0.0821Ã—(273.15+25)2.75L=0

(b)

Interpretation Introduction

Interpretation:

For the given reaction the pressure of the given gas under given conditions and the total pressure under given conditions should be determined.

Concept Introduction:

Balanced Chemical Equation:

The chemical reaction when the number of atoms present in the reactant side of the reaction should be equal to the number and the charge of atoms present in the product side of the reaction which then only be considered as balanced.

Ideal gas equation:

Any gas is described by using four terms namely pressure, volume, temperature and the amount of gas. Thus combining three laws namely Boyle’s, Charles’s Law and Avogadro’s Hypothesis the following equation could be obtained. It is referred as ideal gas equation.

nTPV = RnTPPV = nRTwhere,n = moles of gasP = pressureT = temperatureR = gas constant

Under some conditions gases don not behave like ideal gas that is they deviate from their ideal gas properties. At lower temperature and at high pressures the gas tends to deviate and behave like real gases.

Boyle’s Law:

At given constant temperature conditions the mass of given ideal gas in inversely proportional to its volume.

Charles’s Law:

At given constant pressure conditions the volume of ideal gas is directly proportional to the absolute temperature.

Two equal volumes of gases with same temperature and pressure conditions tend to have same number of molecules with it.

Mole fraction: The mole fraction of denotes the individual presence of the component present in the given chemical reaction.

Consider general equation that contains reactants X and Y then the mole fraction of X is determined as follows,

Mole fraction of Mole fraction of one component = Moles of that componentTotal moles present in the reactionMole fraction of X = Number of moles of XNumber of moles of X + Number of moles of Y

The relationship between partial pressure and Ptotal is

Pi=χiPtotalwhere,Pi=partial pressureχi=molefractionPtotal=Totalpressure

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