Describe the energy transformation when a match burns.

igor_vitrenko [27]

Answer:

The reaction is exothermic (option 4)

Explanation:

P4 + 5O2 → P4O10 + 712 kcal

In chemical reactions heat can be absorbed or released:

⇒in the first case, when heat is absorbed, this is called an endothermic reaction. The products have more energy than the reactants. The reaction requires or absorbs energy from it's surroundings. That means that in this reaction energy , in the form of heat, will be absorbed by the reactants.

⇒ when heat is released, this is called an exothermic reaction. The reactants have more energy than the products. The reaction gives or releases energy to it's surroundings. That means that in this reaction energy , in the form of heat, will be released by the reactants.

in the case of P4 + 5O2 → P4O10 + 712 kcal

We notice that on the right side, which is the product side, there is a positive amount of energy. This means that the energy is released by the the reactants, in this reaction. The reaction is exothermic.

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4 0

3 years ago

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A piece of wood with a density of 0.85 g/cm^3 has a mass of 25 g. what is the volume of the wood?

Karolina [17]

Density = m/v therefore v = m/d v = 25/0.85 v = 29.4117... cm^3 ( = 2.94 * 10^-5 m^3

5 0

3 years ago

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Write the balanced chemical equation for the following reaction. Phases are optional. Solid calcium chlorate decomposes to form

Tanya [424]

Answer:

Ca(ClO₃)₂ (s) → CaCl₂ (s) + 3O₂ (g)

Explanation:

1) Word equation (given)

calcium chlorate (solid) → solid calcium chloride (solid) + oxygen (gas)

2) Chemical formulae of the reactant and products:

Calcium chlorate:

The most common oxidation states of chlorine are -1, +1, +3, +5, +7.

The suffix ate in chlorate means that chlorine atom is with the third lowest oxidation state (counting only the positive states). So, this is +5.

The oxidation state of calcium is +2.

Hence, the chemical formula of calcium chlorate is Ca(ClO₃)₂

Calcium chloride

The suffix ide in chloride means that chlorine is with oxidation state -1. Again the oxidation state of calcium is +2.

Hence, the chemical formula of calcium chloride is CaCl₂

Oxygen

Oxygen gas is a diatomic molecule, so its chemical formula is O₂.

Phases

The symbols s and g (in parenthesis) indicate the solid and gas phases respectively.

3) Chemical equation:

Ca(ClO₃)₂ (s) → CaCl₂ (s) + O₂ (g)

That equation is not balanced becasue the number of O atoms in the reactant side and in the product side are different.

4) Balanced chemical equation:

Add a 3 as coefficient in front of O₂(g), in the product side to balance:

Ca(ClO₃)₂ (s) → CaCl₂ (s) + 3O₂ (g)

Verify that all the atoms are balanced:

Atom Reactant side Product side

Ca 1 1

Cl 2 2

O 3×2 = 6 2×3 = 6

Conclusion: the equation is balanced and the final answer is:

Ca(ClO₃)₂ (s) → CaCl₂ (s) + 3O₂ (g)

5 0

3 years ago

If 4000 g of Fe2O3 reacts, how many moles of CO are needed? (add work)

7nadin3 [17]

Answer:

75.15 mol.

Explanation:

Firstly, we need to write the balanced equation of the reaction:

Fe₂O₃ + 3CO → 2Fe + 3CO₂.

It is clear that 1.0 mole of Fe₂O₃ reacts with 3.0 moles of CO to produce 2.0 moles of Fe and 3.0 moles of CO₂.

∴ Fe₂O₃ reacts with CO with (1: 3) molar ratio.

we need to calculate the no. of moles of (4000 g) of Fe₂O₃:

no. of moles of Fe₂O₃ = mass/molar mass = (4000 g)/(159.69 g/mol) = 25.05 mol.

Using cross multiplication:

1.0 mole of Fe₂O₃ needs → 3.0 moles of CO,

∴ 25.05 mole of Fe₂O₃ needs → ??? moles of CO.

∴ The no. of moles of CO needed = (3.0 mol)(25.05 mol)/(1.0 mol) = 75.15 mol.

5 0

4 years ago

How do polar molecules respond when they are placed between two metal plates, one positively charged and one negatively charged?

kakasveta [241]

Gradpoint

The molecules align to the electric field

5 0

3 years ago

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