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3 years ago

How is enthalpy used to predict whether a reaction is endothermic or exothermic?

1 answer:

8 0

If the enthalpy change is negative, then the reaction is exothermic because heat energy was lost to the surroundings.

If the enthalpy change was positive, then the reaction was endothermic because heat energy was gained from the surroundings!

Hope this helps!! x

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How many moles (of molecules or formula units) are in each sample? 79.34 g cf2cl2?

Alona [7]

From the periodic table:
molecular mass of carbon = 12 grams
molecular mass of fluorine = 18.99 grams
molecular mass of chlorine = 35.5 grams
Therefore:
one mole of CF2Cl2 = 12 + 2(18.99) + 2(35.5) = 120.98 grams
Therefore, we can use cross multiplication to find the number of moles in 79.34 grams as follows:
mass = (79.34 x 1) / 120.98 = 0.6558 moles

Now, one mole contains 6.022 x 10^23 molecules, therefore:
number of molecules in 0.65548 moles = 0.6558 x 6.022 x 10^23
= 3.949 x 10^23 molecules

7 0

3 years ago

Calculate the volume occupied by 272g

cupoosta [38]

The answer for the following problem is mentioned below.

Therefore volume occupied by methane gas is 184.78 × 10^-3 liters

Explanation:

Given:

mass of methane( $CH_{4}$ ) = 272 grams

pressure (P) = 250 k Pa =250×10^3 Pa

temperature(t) = 54°C =54 + 273 = 327 K

Also given:

R = 8.31JK-1 mol-1 ,

Molar mass of methane( $CH_{4}$ ) = 16.0 grams

We know;

According to the ideal gas equation,

P × V = n × R × T

here,

n = m÷M

n =272 ÷ 16

n = 17 moles

Therefore,

250×10^3 × V = 17 × 8.31 × 327

V = ( 17 × 8.31 × 327 ) ÷ ( 250×10^3 )

V = 184.78 × 10^-3 liters

Therefore volume occupied by methane gas is 184.78 × 10^-3 liters

6 0

3 years ago

Which of thes is a property of a substance that is composed of atoms that are held together by ionic bonds?

Svetlanka [38]

Answer: D) It conducts electricity when it is dissolved in water

8 0

2 years ago

Is mass conserved when 200 g of water undergoes a physical change? Use complete sentences to support your answer by explaining h

andrew-mc [135]

Answer:

-200

Explanation:

7 0

3 years ago

Does anyone know this!?

saul85 [17]

Answer:

I don’t know this answer sorry

Explanation:

3 0

2 years ago