Chemistry, 01.03.2021 22:00 0140875

Consider the reaction 2H2(g)+O2(g)→2H2O(l) 2 H 2 ( g ) + O 2 ( g ) → 2 H 2 O ( l ) What is the mass of water, H2O(l) H 2 O ( l ) , produced when 5.70 g g of O2(g) O 2 ( g ) reacts with excess H2(g) H 2 ( g ) ?hen 5.70 g g of O2(g) O 2 ( g ) reacts with excess H2(g) H 2 ( g ) ?

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Answer from: darrell1168

mH₂O = 6.4116 g

Explanation:

Let's write the given reaction:

2H₂ + O₂ > 2H₂O

The problem states that 5.7 g of oxygen reacts with excess hydrogen, hence, the limiting reagent is the oxygen. With this mass of oxygen, we can determine the moles, and then, the moles of water with the mole ratio:

moles = mass / atomic weight AW of O₂ = 16 g/mol

Replacing we have:

moles O₂ = 5.70 / (16 * 2)

moles O₂ = 0.1781 moles

According to the balanced reaction, 1 mole of Oxygen produces 2 moles of water, so we have a mole ratio 1:2, therefore the moles of water would be twice the moles of oxygen:

moles H₂O = 0.1781 * 2 = 0.3562 moles

Finally the mass of water can be calculated solving for the mass from the expression of moles, and using molecular mass of water:

m = moles * MM MM H₂O = 18 g/mol

m = 0.3562 * 18

mH₂O = 6.4116 g

Hope this helps

Answer from: Quest

the missing options are :

(1) lower boiling point and a lower freezing point(2) lower boiling point and a higher freezing point(3) higher boiling point and a lower freezing point(4) higher boiling point and a higher freezing point

answer : the correct answer is option (3) higher boiling point and a lower freezing point

explanation :

when a non volatile solute is added to a solvent like water, it results in elevation of boiling point.

let us find the increase in boiling point of water when cacl₂ is added to water to make a solution of 1 m

step 1 : find molality of the solution

let us assume we have 1 l of solution.

$m = \frac{moles (solute)}{l ( solution)}$

$1 m = \frac{moles (cacl_{2})}{1 l }= 1 mol cacl_{2}$

let us convert this to grams of cacl₂.

molar mass of cacl2 is 111 g/mol

grams of cacl₂ = $1 mol \times \frac{111g}{mol} = 111 g cacl_{2}$

mass of solute = 111 g

assuming density of solution same as water which is 1g/ml we have ,

mass of solution = density * volume

mass of solution = $\frac{1g}{ml} \times 1000 ml = 1000 g$

mass of solution = mass of solvent + mass of solute

mass of solute = 1000g - 111g

mass of solute 889 g = 0.889 kg

the molality of the solution can be calculated as

$molality = \frac{mol (solute)}{kg ( solvent)}$

$molality = \frac{1mol}{0.889kg}$

molality = 1.12 m

step 2 : find boiling point elevation.

the elevation in boiling point is calculated as

$\bigtriangleup t_{b} = i \times k_{b} \times m$

here δtb = boiling point elevation

i = vant hoff factor which is the number of ions formed by the solute .

cacl₂ dissociates as $cacl_{2} \rightarrow ca^{2+} + 2 cl^{-}$

it forms 3 ions . therefore,

i = 3

m = molality which is 1.12 m

kb is constant for a given solvent. for water it is 0.512

$\bigtriangleup t_{b} = 3 \times 0.512 \times 1.12$

$\bigtriangleup t_{b} = 1.7$

the boiling point of water increases by 1.7 °c

step 3: find freezing point depression.

when a non volatile solute is added to water, it results in decrease in freezing point.

the formula to find freezing point depression is

$\bigtriangleup t_{f} = i \times k_{f} \times m$

kf is constant for water and its value is 1.86

$\bigtriangleup t_{f} = 3 \times 1.86 \times 1.12$

$\bigtriangleup t_{f} = 6.2$

the freezing point of water decreases by 6.2 °c

therefore we can say that, the solution will have a higher boiling point and a lower freezing point

Answer from: Quest

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Consider the reaction 2H2(g)+O2(g)→2H2O(l) 2 H 2 ( g ) + O 2 ( g ) → 2 H 2 O ( l ) What is the mass...

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