Label the following as a pure substance or a mixture.

The smallest units of matter that normally CANNOT be broken down are atoms. molecules. cells. phospholipids.

olya-2409 [2.1K]

Answer: atoms

Explanation:

All matter is made up of smaller indivisible particles called atoms. These atoms are the smallest units of matter ACCORDING to the Dalton's Atomic theory.

Molecules are combined atoms, while cells and phospholipids are complex combination of atoms.

Therefore, atoms is the answer

4 0

3 years ago

Fill in the coefficients that will balance the following reaction: a0Ca + a1CO2 + a2O2 → a3CaCO3

VashaNatasha [74]

The chemical equation without coefficients is:

Ca + CO2 + O2 --------> Ca CO3

You can balance that equation by trial an error.

This is the chemical equation balanced:

2Ca + 2CO2 + O2 --------> 2Ca CO3

Count the atoms on each side to check the balance

Atom Left side    right side

Ca    2    2

C    2    2

O 2*2 + 2 = 6    2*3 = 6

Then those are the coefficients:

a0 = 2

a1 = 2

a2 = 1

a3 = 2

6 0

3 years ago

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

......................................

Alinara [238K]

Answer:

Explanation:

yes leon is correct because matter is anything that takes space and also has mass in it.

thks.

5 0

2 years ago

If 250 milliliters of Calcium Hydroxide is titrated with 345 milliliters of 0.75 molarity hydrobromic acid, what is the concentr

Bingel [31]

The balanced neutralization reaction here is:

Ca(OH)2 + 2HBr --> 2H2O + CaBr2

Notice that two moles of Her are required to neutralize every one mole of Ca(OH)2. This means that for however many moles of Her reacted, HALF as many moles of Ca(OH)2 reacted as well.

Moles of HBr reacted = 0.75 M x 0.345 L = 0.259 mol

Moles of Ca(OH)2 reacted = 0.259 mol / 2 = 0.130 mol

Concentration of Ca(OH)2 = 0.130 mol / 0.250 L = 0.52 M

4 0

2 years ago