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3 years ago

Practice

Chemistry

1 answer:

tekilochka [14]3 years ago

5 0

Answer and Explanation:

For each reaction, it is useful to detail which are the reactants (left side of the equation) and which are the products (right side of the equation), to deduce the chemical formulas.

1. Solid lithium reacts with water to produce hydrogen gas and a solution of lithium hydroxide.

Reactants: lithium element in solid-state (Li(s)) and water (H₂O) in the liquid-state. Products: hydrogen gas which is a diatomic molecule (H₂) and lithium hydroxide, which is a base formed by lithium cation Li⁺ and OH⁻ anion (LiOH).

Li(s) + H₂O(l) → H₂(g) + LiOH(aq)

2. Solid sodium reacts with gaseous chlorine to produce sodium chloride.

Reactants: sodium metal in solid-state (Na(s)) and chlorine which is a diatomic gas (Cl₂). Products: sodium chloride, which is a salt formed by sodium and chloride together (NaCl).

Na(s) + Cl₂(g) → NaCl(s)

3. Solid calcium carbonate breaks down into carbon dioxide gas, oxygen gas, and solid calcium.

It is a decomposition reaction, so we have only one reactant: calcium carbonate, which is a salt composed of carbonate anion (CO₃⁻²) and calcium ion (Ca²⁺). Products: carbon dioxide (CO₂), oxygen gas which is diatomic (O₂), and solid calcium (Ca(s)).

CaCO₃(s) → CO₂(g) + O₂(g) + Ca(s)

4. Solid iron(II) sulfate and a solution of barium chloride react to form solid barium sulfate and a solution of iron (II) chloride.

Reactants: iron(II) sulfate which is an ionic compound formed by the sulfate ion (SO₄²⁻) and iron ion (with two positive charges: Fe²⁺), and barium chloride which is a salt of barium ion (Ba²⁺) and two chloride ions (Cl⁻). Products: the salts formed by ion exchange, barium sulfate (BaSO₄), and iron (II) chloride (FeCl₂).

FeSO₄(s) + BaCl₂(aq) → BaSO₄(s) + FeCl₂(aq)

5. Solutions of hydrochloric acid and sodium hydroxide react to produce liquid water with sodium chloride dissolved in it.

It is the classical neutralization reaction. Reactants: hydrochloric acid (HCl) and the strong base sodium hydroxide (NaOH). Products: water (H₂O) and the salt formed by the anion provided by the acid (Cl⁻) and the cation provided by the base (Na⁺): NaCl.

HCl(aq) + NaOH(aq) → H₂O(l) + NaCl(aq)

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Which of the following is likely to be true about the ΔH for this reaction?

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Answer: Option (a) is the correct answer.

Explanation:

Enthalpy is defined as the total amount of heat present in a system.

When there is bond formation in a chemical reaction then it means energy is released. Hence, the reaction is exothermic in nature and $\Delta H$ < 0 or negative.

On the other hand, when breaking of bonds occurs then energy is absorbed by the system. Hence, the reaction is endothermic in nature and $\Delta H$ > 0 or positive.

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This means atoms are coming close to each other and hence, there is occurrence of bond formation. As a result, energy will be released to the surroundings.

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SOLVE A 4.80-gram piece of magnesium displaces 2.76 mL of water when it is placed in a graduated cylinder. What is the density o

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Answer:

Density = 1.74 gm/mL

Explanation:

Given that:

Mass of piece of Magnesium = 4.80 grams

The volume displaced by this piece = 2.76mL

Let us learn about a property:

Volume of water displaced by a substance when immersed in the water is equal to the Volume of the substance itself.

So, volume of the piece of Magnesium = 2.76 mL

To find:

Density of magnesium = ?

Solution:

Let us have a look at the formula for Density of a Substance:

Density of a substance is given as the ratio of mass of substance and the volume of that mass of substance.

i.e.

$Density = \dfrac{Mass}{Volume}$

Putting the given values:

$Density = \dfrac{4.80}{2.76}\\\Rightarrow \bold{Density = 1.74\ gm/mL}$

So, the answer is:

Density of Magnesium = 1.74 gm/mL

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Answer:

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Explanation:

Applying,

Q = CΔT................ equation 1

Where Q = amount of heat, C = Heat capacity, ΔT = temperature rise.

From the question,

Given: C = 62.6 J/K, ΔT = 1.20°C

Substitute these values into equation 1

Q = 62.6(1.20)

Q = 75.12 J

Hence the amount of heat it absorbed is 75.12 J

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