Question

please show me how to get the correct answers in preperation for my upcoming exam

16.) 868 18.) 33.9kj 19.) 179

P L ULUCUL COM PICCICUCI Sument Uldisweise uuesti 1) When 0.800 grams of NaOH is dissolved in 100.0 grams of water, the temperature of the Solution increases from 25.00 °C to 27.06 °C. The amount of heat absorbed by the water is_ J. (The specific heat of water is 4.18 J/g-°C.)

Answer 1

Solution 16)

Given mass of NaOH = 0.800 gm

Mass of water = 100.0 gm

Nass of solution = mass of NaOH + mass of water = 0.800 + 100 = 100.8 g

Mass of solution = 100.8 g

T₁ = 25.00^οC & T₂ = 27.06^οC

∆T = T₂ – T₁ = 27.06 – 25.00 = 2.06 ^οC

∆T = 2.06 ^οC

specific heat of water = 4.18 J/g. ^οC

amount of Heat absorbed by water is given as

Q = mcΔT

m = mass of solution, c = specific heat of water & ΔT = change in temp of water

Q = 100.8 g x 4.18 J/g. ^οC x 2.06 ^οC

Q = 867.96 J

Q = 868 J

Solution 18 )

Given

molar heat of vaporization ∆H_vap = 40.7 KJ per mole

40.7 KJ heat is required to boil 1 mole of water at 100^οC

Mass of water = 15 g molar mass of water = 18.01 g /mol

Number of moles of water = (15g) / (18.01 g /mol ) =0.8329 moles

Number of moles of water = 0.8329 moles

Molar heat of vaporization of water = 40.7 KJ per mole then how much heat would be needed to boil 0.8329 moles of liquid water to vapor

0.8329 moles x 40.7 KJ / 1 mole of H₂O = 33.90 KJ

The amount of heat required to convert 15.0 g of liquid water to vapor = 33.9 KJ

Solution 19)

Given

Mass of C₂H₆ = 120 g

Molar mass of C₂H₆ = 30 g/mol

So number of mole of C₂H₆ = 120 g / 30 g/mol = 4 moles

So number of mole of C₂H₆ = 4 moles

Combustion of ethane is

2C₂H₆ + 7 O₂ = 4CO₂ + 6H₂O

From above reaction we says that 2 mole of C₂H₆ produce 4 mole of CO₂ so mole CO₂ = 4/2 mole of C₂H₆

Number of mole of CO₂ = 4/2 x 4 =8 mole

Number of mole of CO₂ =8 mole

Now molar volume of any gas = 22.414 L/mol at STP

Volume of CO₂ gas = mole of CO₂ x molar volume of CO₂ gas at STP

Volume of CO₂ gas = 8 mole x 22.414 L /mol

Volume of CO₂ gas = 179.31 L