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yKpoI14uk [10]
3 years ago
10

Question 1 . . Which of the following is not an example of a chemical change?. . A candle burning. . Cake baking. . Glass breaki

ng. . A nail rusting. . Question 2 . . All of the following require breaking and forming chemical bonds except:. . Freezing ice. . A plant decaying. . A piece of silver tarnishing. . Roasting a marshmallow. . Question 3 (Multiple Choice Worth 2 points). . Chemical changes. . are only caused through burning a material.. . only occur to weak materials.. . change the identity of a substance.. . do not affect the identity of a sub
Chemistry
1 answer:
musickatia [10]3 years ago
3 0
For question 1, the correct answer is a glass breaking because this process involves only a physical change. The identity of the glass was not changed. For question 2, the correct answer is freezing ice because the bonds in a phase change are not broken down or are formed. For question 3, the correct answer is the last option.  Chemical changes <span>change the identity of a substance.</span>
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Hydrogen iodide, HI, is formed in an equilibrium reaction when gaseous hydrogen and iodine gas are heated together. If 20.0 g of
Kaylis [27]

Answer: D. 19.9 g hydrogen remains.

Explanation:

To calculate the moles, we use the equation:

\text{Number of moles}=\frac{\text{Given mass}}{\text {Molar mass}}

a) moles of H_2

\text{Number of moles}=\frac{20.0g}{2g/mol}=10.0moles

b) moles of I_2

\text{Number of moles}=\frac{20.0g}{254g/mol}=0.0787moles

H_2(g)+I_2(g)\rightarrow 2HI(g)

According to stoichiometry :

1 mole of I_2 require 1 mole of H_2

Thus 0.0787 moles of l_2 require=\frac{1}{1}\times 0.0787=0.0787moles of H_2

Thus l_2 is the limiting reagent as it limits the formation of product and H_2 acts as the excess reagent. (10.0-0.0787)= 9.92 moles of H_2are left unreacted.

Mass of H_2=moles\times {\text {Molar mass}}=9.92moles\times 2.01g/mol=19.9g

Thus 19.9 g of H_2 remains unreacted.

5 0
2 years ago
Hydrofluoric acid, hf, has a ka of 6.8 × 10−4. what are [h3o+], [f−], and [oh−] in 0.710 m hf?
STALIN [3.7K]

Answer:

[H₃O⁺] = [F⁻] = 2.2 x 10⁻² M. & [OH⁻] = 4.55 x 10⁻¹³.

Explanation:

  • For a weak acid like HF, the dissociation of HF will be:

<em>HF + H₂O ⇄ H₃O⁺ + F⁻.</em>

[H₃O⁺] = [F⁻].

<em>∵ [H₃O⁺] = √Ka.C,</em>

Ka = 6.8 x 10⁻⁴, C = 0.710 M.

∴ [H₃O⁺] = √Ka.C = √(6.8 x 10⁻⁴)(0.710) = 2.197 x 10⁻² M ≅ 2.2 x 10⁻² M.

<em>∴ [H₃O⁺] = [F⁻] = 2.2 x 10⁻² M.</em>

<em></em>

∵ [H₃O⁺][OH⁻] = 10⁻¹⁴.

<em>∴ [OH⁻] = 10⁻¹⁴/[H₃O⁺]</em> = 10⁻¹⁴/(2.2 x 10⁻²) = <em>4.55 x 10⁻¹³.</em>

6 0
2 years ago
A sealed reaction vessel initially contains 1.113×10-2 moles of water vapor and 1.490×10-2 moles of CO(g).
Molodets [167]

Answer:

Kc =\frac{[8.326x10-3]^{1} }{[1.113x10-2]^{1}[1.490x10-2]^{1}  }

Kc = 50.2059

Explanation:

1. Balance the equation

2. Use the Kc formula

Remember that pure substances, like H2 are not included on the Kc formula

4 0
3 years ago
What is the enthalpy of fusion of water?
malfutka [58]

Answer:

d-  334 kJ/g.

Explanation:

You can detect it from the units of the different choices.

a- has the unit J/g.°C that is the unit of the specific heat capacity (c).

b- has the unit Kelvin that is the unit of temperature.

c- has the unit g/mol which is the unit of the molar mass.

d- has the unit kJ/g which is the unit of the enthalpy divided by the no. of rams that is the specific entha;py of fusion.

<em>So, the right choice is: d-  334 kJ/g.</em>

5 0
3 years ago
What is the product of a force and the time during which the force acts
ELEN [110]

Impulse is the product of a force and the time during which that force acts on a body.

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