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3 years ago

How do you know that a combustion reaction is exothermic

Chemistry

1 answer:

kap26 [50]3 years ago

5 0

When you burn wood it gives off heat. that heat is what makes the combustion reaction exothermoc

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Elena held a rock weighing 1 N in her hand. The rock has no velocity. KE________?

nignag [31]

KE = 0

<h3>Further explanation </h3>

Energy is the ability to do work

Energy because its motion is expressed as Kinetic energy (KE) which can be formulated as:

$\large{\boxed{\bold{KE=\frac{1}{2}mv^2}}}$

So for two objects that have the same speed, the greater the mass of the object, the greater the kinetic energy

The stone in hand is in a motionless state (at rest) so that its velocity (v) = 0, so it has no kinetic energy

But this stone can have potential energy that is gained due to its height

5 0

3 years ago

Natural atom of the same element may have the same _________?

Minchanka [31]

Answer:B

Explanation:

4 0

3 years ago

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what is the molar mass of a gaseous flouride of sulfur containing 70.4% F and having a density of approximately 4.5g/L at 20 deg

zlopas [31]

Answer:

The molar mass is 180.2 g/mol

Explanation:

Step 1: Data given

% of F = 70.4 %

Density = 4.5 g/L

Temperature = 20 °C

Pressure = 1 atm

Step 2: Calculate the number of moles

PV = nRT

⇒ with P = the pressure = 1.00 atm

⇒ with V = the volume = Assume this is 1L

⇒ with n = the number of moles = TO BE DETERMINED

⇒ R = the gas constant = 0.08206 L*atm/K*mol

⇒ T = the temperature : 20°C = 293 Kelvin

1 atm*1L= n(0.08206 L-atm/mol-K)*(293 K)

n = 0.04159 moles

Step 3: Calculate molar mass

Molar mass = Mass / moles

4.5 grams / 0.04159 moles = 108.2 g/mol

Step 4: Calculate moles of F

Moles = Mass / molar mass

Moles F = 70.4 g / 19 g/mol

Moles F = 3.70 moles

Moles S = 29.6g / 32.07 g/mol

Moles S = 0.923 moles S

Step 5: Divide by the smallest amount of moles

F = 3.70 / 0.923 = 4

S = 0.923 / 0.923 = 1

The empirical formula is SF4

The molar mass of SF4 = 32.07 + 4*19 = 108.07 g/mol

This means the empirical formula is the same as the molecular formula SF4

The molar mass is 180.2 g/mol

4 0

3 years ago

The solubility product of PbI2 is 7.9x10^-9. What is the molar solubility of PbI2 in distilled water?

Agata [3.3K]

Answer: The molar solubility of $PbI_2$ is $1.25\times 10^{-3}mol/L$

Explanation:

Solubility is defined as the maximum amount of solute that can be dissolved in a solvent at equilibrium.

Solubility product is defined as the product of concentration of ions present in a solution each raised to the power its stoichiometric ratio.

The balanced equilibrium reaction for the ionization of calcium fluoride follows:

$PbI_2\rightleftharpoons Pb^{2+}+2I^-$

s 2s

The expression for solubility constant for this reaction will be:

$K_{sp}=[Pb^{2+}][I^-]^2$

We are given:

$K_{sp}=7.9\times 10^{-9}$

Putting values in above equation, we get:

$7.9\times 10^{-9}=(s)\times (2s)^2\\\\7.9\times 10^{-9}=4s^3\\\\s=1.25\times 10^{-3}mol/L$

Hence, the molar solubility of $PbI_2$ is $1.25\times 10^{-3}mol/L$

3 0

3 years ago

Whose model of the atom did J.J. Thomson prove to be incorrect with his Cathode-Ray tube experiments?

Brut [27]

JJ Thomson proved John Dalton's theory wrong, as Thomson discovered the electron. This showed that there were particles that were smaller than an atom, despite Dalton claiming that the atom is the smallest unit of matter.

7 0

3 years ago

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