What is a well-tested, explanation that unifies a broad range of observations and hypotheses

kogti [31]

1 CH4 (g) + 2 O2 (g) -----> CO2 (g) + 2H2O(l) ΔH= - 890 kJ
1 mol 2 mol
1)  If ΔH has minus, it means "release". We need only "release" choices.<span>
2) From reaction
1 mol </span>CH4 (g)  "releases"  ΔH= - 890 kJ - We do not have this choice.

2 mol  O2 (g)   "release" ΔH= - 890 kJ, so
1 mol  O2 (g)   "release" ΔH= - 445 kJ
Correct answer is B.

3 0

3 years ago

Read 2 more answers

A 1.25 g sample of aluminum is reacted with 3.28 g of copper (II) sulfate. What is the limiting reactant?

mestny [16]

Answer:

d. Copper (II) sulfate

Explanation:

Given data:

Mass of Al = 1.25 g

Mass of CuSO₄ = 3.28 g

What is limiting reactant = ?

Solution:

Chemical equation:

2Al + 3CuSO₄ → Al₂ (SO₄)₃ + 3Cu

Number of moles of Al:

Number of moles = mass/molar mass

Number of moles = 1.25 g/ 27 g/mol

Number of moles = 0.05 mol

Number of moles of CuSO₄:

Number of moles = mass/molar mass

Number of moles = 3.28 g/ 159.6 g/mol

Number of moles = 0.02 mol

now we will compare the moles of reactant with product.

Al : Al₂ (SO₄)₃

2 : 1

0.05 : 1/2×0.05=0.025 mol

Al : Cu

2 : 3

0.05 : 3/2×0.05 = 0.075 mol

CuSO₄ : Al₂ (SO₄)₃

3 : 1

0.02 : 1/3×0.02=0.007 mol

CuSO₄ : Cu

3 : 3

0.02 : 0.02

Less number of moles of reactants are produced by CuSO₄ thus it will act as limiting reactant.

7 0

3 years ago

How many moles of water are<br> in 1.23x10¹8 water molecules?<br> [ ? ]×10[?]

Sergio [31]

Answer:

2.04 x 10⁻⁶ moles H₂O

Explanation:

To find the moles H₂O, you need to multiply the given value by Avogadro's Number. This number is a ratio between molecules and moles, thus granting you the way to convert between both units. It is important to arrange the ratio in a way that allows for the cancellation of units. The final answer should have 3 sig figs to match the sig figs of the given value (1.23 x 10¹⁸ molecules).

Avogadro's Number:

6.022 x 10²³ molecules = 1 mole

1.23 x 10¹⁸ molecules H₂O 1 mole
--------------------------------------- x ------------------------------------- =
6.022 x 10²³ molecules

= 2.04 x 10⁻⁶ moles H₂O

5 0

2 years ago

How many moles are in a sample of 4.57 x 10^24 atoms of neon (Ne)?

balu736 [363]

Hello!

To find the number of moles in a sample of 4.57 x 10^24 atoms, we need to use Avogadro's number, which is 1 mole = 6.02 x 10^23.

To find how many moles, we divide the given sample by Avogadro's number.

(4.57 x 10^24) / (6.02 x 10^23) ≈ 7.59136

Using the amount of significant figures given (3), the answer is 7.59 moles of neon (Ne).

4 0

3 years ago

ryan is a chemistry student that enjoys hot tea. he wants to determine how much ice is needed to cool 250.0 ml of tea to an opti

mestny [16]

Ryan calculates that he requires 4 ice cubes for 250mL of hot tea to reach the optimal drinking temperature by using the specific heat capacity of tea.

A substance's potential to hold heat is indicated by its specific heat capacity. This substance size reflects the amount of heat required to raise a certain volume of a material's temperature by one Kelvin. Specific heat capacity is a distinguishing feature of every substance and is useful for material identification.

Given:

Final temperature of system is 57.8℃

dT1 = 79.1 - 57.8 = 21.3℃

dT2 = 0 - (-8.33) = 8.33℃

dT3 = 57.8 - 0 = 57.8℃

Mass of tea, m1 = 250.0mL = 250.0g = 0.250kg

Specific heat capacity of tea, C1 = 4186 J/kg℃ = Specific heat capacity of water

Specific heat capacity of ice, Ci = 2090 J/kg℃

Mass of each ice cubes, m of i = 18.8g

Latent heat of fusion of ice, Lf = 334 kJ/kg

To find:

No. of ice cubes required = ?

Calculations:

Suppose equilibrium temperature is T, then

Heat released by Tea = Heat gained by Ice

Q1 = Q2

m1x C1x dT1 = mi x Ci x dT2 + mi x Lf + mi x Cw x dT3

0.250x 4186 x 21.3 = mi x (2090 x 8.33 + 3.34 x $10^4$ + 4186 x 57.8)

mi = 0.250 x 4186 x 21.3 / (2090 x 8.33 + 3.34 x $10^4$ + 4186 x 57.8)

mi = 0.0761kg = 76.1g

Mass of ice required = 76.1g

Number of ice cube required will be:

n = Total mass of ice/mass of each ice cube

n = 76.1/18.8

n = 4.04 ice cubes = 4.0 ice cubes

Result:

Ryan requires 4 ice cubes to bring 250mL of hot tea to the optimal drinking temperature.

Learn more about Specific heat capacity here:

brainly.com/question/24265493

#SPJ4

7 0

2 years ago