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3 years ago

DNA samples should not be stored where?

Chemistry

2 answers:

garri49 [273]3 years ago

8 0

Answer:

in the brain

Explanation:

Anton [14]3 years ago

6 0

Answer:

in the brain

Explanation:

it is bad and will cause harm

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43. Use Table 3-1 to identify a substance that undergoes a

LuckyWell [14K]

Answer:

Oxygen, and from solid to liquid. This is because oxygen's melting point is at -218°C. Melting point refers to the temperature where heat causes particles to vibrate with sufficient energy to break the solid structure, so for oxygen this means it's being turned into a liquid.

4 0

3 years ago

A 50.0-ml sample of 0.50 m hcl is titrated with 0.50 m naoh. what is the ph of the solution after 28.0 ml of naoh have been adde

hram777 [196]

The pH of the solution after addition of 28 mL of NaOH is added to HCl is $\boxed{{\text{0}}{\text{.85}}}$ .

Further Explanation:

The proportion of substance in the mixture is called concentration. The most commonly used concentration terms are as follows:

1. Molarity (M)

2. Molality (m)

3. Mole fraction (X)

4. Parts per million (ppm)

5. Mass percent ((w/w) %)

6. Volume percent ((v/v) %)

Molarity is a concentration term that is defined as the number of moles of solute dissolved in one litre of the solution. It is denoted by M and its unit is mol/L.

The formula to calculate the molarity of the solution is as follows:

${\text{Molarity of solution}}=\dfrac{{{\text{Moles}}\;{\text{of}}\;{\text{solute}}}}{{{\text{Volume }}\left({\text{L}} \riht){\text{ of solution}}}}$

......(1)

Rearrange equation (1) to calculate the moles of solute.

${\text{Moles}}\;{\text{of}}\;{\text{solute}}=\left( {{\text{Molarity of solution}}}\right)\left({{\text{Volume of solution}}}\right)$ ......(2)

Substitute 0.50 M for the molarity of solution and 50 mL for the volume of solution in equation (2) to calculate the moles of HCl.

$\begin{aligned}{\text{Moles}}\;{\text{of}}\;{\text{HCl}}&= \left({{\text{0}}{\text{.50 M}}}\right)\left( {{\text{50 mL}}} \right)\left( {\frac{{{\text{1}}{{\text{0}}^{ - 3}}{\text{ L}}}}{{{\text{1 mL}}}}} \right)\\&= 0.02{\text{5 mol}}\\\end{aligned}$

Substitute 0.50 M for the molarity of solution and 28 mL for the volume of solution in equation (2) to calculate the moles of NaOH.

$\begin{aligned}{\text{Moles}}\;{\text{of}}\;{\text{NaOH}}&=\left( {{\text{0}}{\text{.50 M}}} \right)\left( {{\text{28 mL}}} \right)\left( {\frac{{{\text{1}}{{\text{0}}^{ - 3}}{\text{ L}}}}{{{\text{1 mL}}}}}\right)\\&= 0.014{\text{ mol}}\\\end{aligned}$

The reaction between HCl and NaOH occurs as follows:

${\text{NaOH}} + {\text{HCl}} \to {\text{NaCl}} + {{\text{H}}_2}{\text{O}}$

The balanced chemical reaction indicates that one mole of NaOH reacts with one mole of HCl. So the amount of remaining HCl can be calculated as follows:

$\begin{aligned}{\text{Amount of HCl remaining}}&= 0.02{\text{5 mol}} - 0.01{\text{4 mol}}\\&= {\text{0}}{\text{.011 mol}} \\\end{aligned}$

The volume after the addition of NaOH can be calculated as follows:

$\begin{aligned}{\text{Volume of solution}} &= {\text{50 mL}} + {\text{28 mL}}\\&= {\text{78 mL}}\\\end{aligned}$

Substitute 0.011 mol for the amount of solute and 78 mL for the volume of solution in equation (1) to calculate the molarity of new HCl solution.

$\begin{aligned}{\text{Molarity of new HCl solution}}&= \left({{\text{0}}{\text{.011 mol}}} \right)\left( {\frac{1}{{{\text{78 mL}}}}}\right)\left( {\frac{{{\text{1 mL}}}}{{{{10}^{ - 3}}\;{\text{L}}}}} \right)\\&= 0.1410{\text{2 M}}\\&\approx {\text{0}}{\text{.141 M}}\\\end{aligned}$

pH:

The acidic strength of an acid can be determined by pH value. The negative logarithm of hydronium ion concentration is defined as pH of the solution. Lower the pH value of an acid, the stronger will be the acid. Acidic solutions are likely to have pH less than 7. Basic or alkaline solutions have pH more than 7. Neutral solutions have pH equal to 7.

The formula to calculate pH of an acid is as follows:

${\text{pH}}=- {\text{log}}\left[ {{{\text{H}}^ + }}\right]$ ......(3)

Here,

$\left[{{{\text{H}}^ + }}\right]$ is hydrogen ion concentration.

HCl is a strong acid so it dissociates completely. So the concentration of also becomes 0.141 M.

Substitute 0.141 M for $\left[{{{\text{H}}^ + }}\right]$ in equation (3).

$\begin{aligned}{\text{pH}}&= - {\text{log}}\left({0.141} \right)\\&=0.85\\\end{aligned}$

So the pH of the solution is 0.85.

Learn more:

1. Which indicator is best for titration between HI and ? brainly.com/question/9236274

2. Why is bromophenol blue used as an indicator for antacid titration? brainly.com/question/9187859

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Acid-base titrations

Keywords: molarity, pH, HCl, NaOH, 0.85, 0.141 M, moles of HCl, moles of NaOH, 50 mL, 0.50 M, 28 mL, 0.025 mol, 0.014 mol, 0.011 mol, 78 mL.

4 0

3 years ago

Read 2 more answers

Write the electron configuration for Silicon

morpeh [17]

Answer:

Si₁₄ = 1s² 2s² 2p⁶ 3s² 3p²

Explanation:

Silicon is present in group 14 of periodic table.

It is blue-gray color metalloid.

Its atomic mass is 28 g/mol.

It is mostly used to make allow.

The most important alloy are Al-Si and Fe-Si. These are used to make different machine tools, transformer plates, engine etc.

Its atomic number is 14 and electronic configuration can be written as,

Electronic configuration:

Si₁₄ = 1s² 2s² 2p⁶ 3s² 3p²

The noble gas electronic configuration or abbreviated electronic configuration can also be written.

Si₁₄ = [Ne] 3s² 3p²

The atomic number of neon is 10. Its electronic configuration is,

Ne₁₀ = 1s² 2s² 2p⁶

That's why we write [Ne] for 1s² 2s² 2p⁶ in abbreviated electronic configuration of Si.

5 0

3 years ago

What does the law of the conservation of momentum state?

UNO [17]

Answer:

The conservation of momentum states that, within some problem domain, the amount of momentum remains constant; momentum is neither created nor destroyed, but only changed through the action of forces as described by Newton's laws of motion. ... Momentum is conserved in all three physical directions at the same time.

6 0

3 years ago

´ Identify the independent, dependent, and controlled variables in your experiment which is how does adding salt affect the free

Margaret [11]

<span>An independent variable is a variable that is not affected in the experiment. It is what experimenter controls. Here, the concentration of salt is the independent variable.
On the other side, a dependent variable is called dependent because it depends on the independent variables. It is what is affected and observed during the experiment. Here, the freezing point of water is affected and, thus, it is the dependent variable.
A controlled variable is a variable that must remain unchanged (must be constant) during the experiment so that the effect on the dependent variable depends only on the independent variable. Here, the volume of water must be constant, so it is the controlled variable.

</span>

7 0

4 years ago