Why does a chemical equation be balanced?

Name the two products when calcium carbonate (CaCO3) is heated

trapecia [35]

Answer:

The products are Calcium oxide and Carbon dioxide.

Explanation:

When calcium carbonate is heated, thermal decomposition occurs.

Calcium calcium → Calcium oxide + Carbon dioxide

3 0

2 years ago

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What volume of 0.307 m naoh must be added to 200.0ml of 0.425m acetic acid (ka = 1.75 x 10-5 ) to produce a buffer of ph = 4.250

Blababa [14]

The buffer solution target has a pH value smaller than that of pKw (i.e., pH < 7.) The solution is therefore acidic. It contains significantly more protons $\text{H}^{+}$ than hydroxide ions $\text{OH}^{-}$ . The equilibrium equation shall thus contain protons rather than a combination of water and hydroxide ions as the reacting species.

Assuming that $x \; \text{L}$ of the 0.307 $\text{mol} \cdot \text{dm}^{-3}$ sodium hydroxide solution was added to the acetic acid. Based on previous reasoning, $x$ is sufficiently small that acetic acid was in excess, and no hydroxide ion has yet been produced in the solution. The solution would thus contain $0.2000 \times 0.425 - 0.307 \; x = 0.085 - 0.307 \; x$ moles of acetic acid and $0.307 \; x$ moles of acetate ions.

Let $\text{HAc}$ denotes an acetic acid molecule and $\text{Ac}^{-}$ denotes an acetate ion. The RICE table below resembles the hydrolysis equilibrium going on within the buffer solution.

$\begin{array}{lccccc}\text{R} & \text{HAc} & \leftrightharpoons & \text{H}^{+} & + & \text{Ac}^{-}\\\text{I} & 0.085 - 0.307 \; x& & 0 & & 0.307 \; x\\\end{array}$

The buffer shall have a pH of 4.250, meaning that it shall have an equilibrium proton concentration of $10^{4.250}\; \text{mol}\cdot \text{dm}^{-3}$ . There were no proton in the buffer solution before the hydrolysis of acetic acid. Therefore the table shall have an increase of $10^{-4.250}\;\text{mol}\cdot \text{dm}^{-3}$ in proton concentration in the third row. Atoms conserve. Thus the concentration increase of protons by $10^{-4.250}\;\text{mol}\cdot \text{dm}^{-3}$ would correspond to a decrease in acetic acid concentration and an increase in acetate ion concentration by the same amount. That is:

$\begin{array}{lcccccc}\text{R} & \text{HAc} & \leftrightharpoons & \text{H}^{+} & + & \text{Ac}^{-}\\\text{I} & 0.085 - 0.307 \; x& & 0 & & 0.307 \; x\\\text{C} & - 10^{-4.250} & & +10^{-4.250} & & +10^{-4.250} \\\text{E} & 0.085 - 10^{-4.250} - 0.307 \; x& & 10^{-4.250} & & 10^{-4.250} + 0.307 \; x\end{array}$

By definition:

$\text{K}_{a} = [\text{H}^{+}] \cdot [\text{Ac}^{-}] / [\text{HAc}]\\\phantom{\text{K}_{a}} = 10^{-4.250} \times (10^{-4.250} + 0.307 \; x) / (0.085 - 10^{-4.250} - 0.307 \; x)$

The question states that

$\text{K}_{a} = 1.75 \times 10^{-5}$

such that

$10^{-4.250} \times (10^{-4.250} + 0.307 \; x) / (0.085 - 10^{-4.250} - 0.307 \; x) = 1.75 \times 10^{-5}\\6.16 \times 10^{-5} \; x = 1.48 \times 10^{-6}\\x = 0.0241$

Thus it takes $0.0241 \; \text{L}$ of sodium hydroxide to produce this buffer solution.

6 0

2 years ago

Carbon burns in the presence of oxygen to give carbon dioxide. Which chemical equation describes this reaction?

Alex73 [517]

Your answer is B.
Because it says that that carbon burns in presence of oxygen (C+O) which is equal ( => ) to Carbon Dioxide ( $CO_{2}$ )

3 0

3 years ago

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Substance X has a fixed volume, and the attraction between its particles is strong. Substance Y has widely spread out particles

ycow [4]

Answer: Option (d) is the correct answer.

Explanation:

In solids, molecules are held together by strong intermolecular forces of attraction. As a result, they are unable to move from their initial position and can only vibrate at their mean position.

Hence, a solid has definite shape and volume. Solids cannot be compressed.

Whereas in plasma, molecules are hot ionized which include positively charged ions and negatively charged electrons. They collide much more rapidly with each other and are widely spreaded out.

Therefore, they occupy the volume of container in which they are placed. Plasma can be compressed.

Thus, we can conclude that substance X is a solid and substance Y is a plasma.

6 0

2 years ago

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Describe relationships between molecules atoms and a grain of sugar

Contact [7]

The relationships between molecules atoms and a grain of sugar is the combination of atoms to molecules and the combination of molecules to a compound.

<u>Explanation:</u>

Atom is the foreground to the existence of matter and matter is just another huge combination of atoms. The presence of neutrons, protons and electrons are the important structures of atoms and these atoms are merged to build a molecule.

The relationships between molecules atoms and a grain of sugar is the combination of atoms to molecules and the combination of molecules to a compound.

Molecules are brought together with positive and negative parts of protons and electrons to form bonds and compounds. And compounds come up with elements which connects all these atoms.

3 0

2 years ago