How does the density of ice compare with that of liquid water? What evidence can you cite to support your answer?

Leokris [45]

The answer to this question is 2 and 3

5 0

3 years ago

What are some complex impurities found in water that are hard to detect and remove? How are they removed and detected? Please an

liubo4ka [24]

This are my answers to your quesion

When working in laboratories and hospitals, it’s crucial that any contaminants found in water are removed immediately, before they cause any damage.

Each impurity carries its own risks to chemical and biological research, not to mention the detrimental effect they cause to the quality of pure water. Here we discuss the 8 main types of water contaminants, and how they can be prevented.

1. Microorganisms

Bacteria, algae and fungi all regularly interfere with sterile research applications. Bacteria can adversely influence cell and tissue culture by competing at enzyme-active sites on substrates.

If free-floating bacteria form biofilms on surfaces, they can be extremely difficult to remove. These biofilms can grow for several years, spontaneously releasing bursts of bacteria, along with their associated endotoxins and nucleases.

These nucleases then break down DNA and RNA in samples, and the endotoxins will have a negative effect on the growth and function of cells.

2. Viruses

Viruses – referred to as non-living nucleic acids – adversely affect tissue and cell growth. They’re extremely small, with most of them falling between 0.01 – 0.3 microns, and they can survive for long periods of time. Once they’ve been spotted in water, they should be removed as soon as possible.

3. Pyrogens

For mammalian cell cultures, and the preparation of solutions or devices that will later have contact with humans and other mammals, it’s crucial that the water used is pyrogen-free.

The most significant component of pyrogens – a form of endotoxin – is lipopolysaccharides (LPS), which is derived from Gram-negative bacteria walls. If LPS gets into the blood or spinal fluid, it can be toxic and cause a fever.

4. Dissolved Inorganic Ions

Silicates, chlorides, calcium, fluorides, magnesium, phosphates, bicarbonates, sulphates, nitrates and ferrous compounds are all forms of dissolved inorganic ions.

The instability in water caused by these ions will negatively influence chemical and biological reactions. Results include the formation of protein-protein and protein-lipid interaction, altering enzymatic activity, and delaying the growth of cells and tissue.

5. Dissolved Organic Compounds

These are derived from animal and plant decay, in addition to any human activities that involve the introduction of alcohol, protein, pesticides, chloramine, herbicides or detergents into the environment.

Dissolved organic compounds interfere with high performance liquid chromatography (HPLC), gas chromatography and fluoroscopy.

6. Dissolved Gases

Water contains naturally dissolved carbon dioxide, nitrogen and oxygen, but these gases can alter the pH of lab water, which upsets the ionic balance. Concentrations of oxygen and nitrogen can affect the rate of biochemical reactions; and high concentration of dissolved gases can cause a bubble formation, which obstructs the flow through chromatography columns and micro-channels.

Dissolved carbon dioxide raises water acidity, reducing the capacity of ion exchange resins in DI systems.

7. Suspended Particles

When large suspended particles of clay, sand, silt or vegetation between 1 – 10µm are found in water, they cause turbidity and settle at the bottom.

Suspended particles can foul reverse osmosis membranes, filters and chromatography columns, especially if the system stems from a reservoir or tank within the building.

8. Colloidal Particles

Colloidal particles are much smaller than suspended particles, at just 0.01 – 1.0µm, and they don’t settle.

Colloidal particles regularly interfere with analytical techniques, and bypass ion exchange resins, which result in lower resistivity in DI water.

How to Prevent Contaminants

The main way to prevent and remove contaminants are through water purification systems. Different technologies have been created, each specialising in the removal of specific contaminants.

For example, whilst the process of distillation won’t remove ionised gases, inorganic ions or dissolved non-ionised gases, they will filter out bacteria and pyrogens.

Reverse osmosis (RO) is hailed as one of the most effective ways of removing contaminants, as this process removes up to 99% of impurities in water. Dissolved organics and ionics, suspended impurities, bacteria and pyrogens are all removed from water when RO is used.

To conclude, contaminants can be very damaging to water. Once found, they should be removed as soon as possible, using the most effective form of water purification technology.

4 0

3 years ago

2. (8 pts) Boric acid (H3BO3) has three hydrogens in a molecule, but effectively acts as a monoprotic acid (Ka = 5.8∙10-10), sin

Andrew [12]

Answer:

7.85 g H₃BO₃

2.92 g NaOH

Explanation:

The strategy for solving this question is to first utilize the Henderson- Hasselbach equation to calculate the ratio of conjugate base concentration to weak acid:

pH = pKa + log [A⁻]/ [HA]

In this case:

pH = pKa + log [H₂BO₃⁻]/[H₃BO₃]

We know pH and indirectly pKa ( = - log Ka ).

9.00 = -log(5.8 x 10⁻¹⁰) + log [H₂BO₃⁻]/[H₃BO₃]

9.00 = 9.24 + log [H₂BO₃⁻]/[H₃BO₃]

log [H₂BO₃⁻]/[H₃BO₃] = - 0.24

taking inverse log function to both sides of the equation:

[H₂BO₃⁻]/[H₃BO₃] = 10^-0.24 = 0.58

We are also told we want to have a total concentration of boron of 0.200 mol/L, and if we call x the concentration of H₂BO₃⁻ and y the concentration of H₃BO₃, it follows that:

x + y = 0.200 ( since we have 1 Boron atom per formula of each compound)

and from the Henderson Hasselbach calculation, we have that

x / y = 0.58

So we have a system of 2 equations with two unknowns, which when solved give us that

x = 0.073 and y = 0.127

Because we are told the volume is one liter it follows that the number of moles of boric acid and the salt are the same numbers 0.073 and 0.127

gram boric acid = 0.127 mol x molar mass HBO₃ = 0127 mol x 61.83 g/mol

= 7.85 g boric acid

grams NaOH = 0.073 mol x molar mass NaOH = 0.073 x 40 g/mol

= 2.92 g NaOH

4 0

4 years ago

Using the word bank explain why increasing the temperature increases the rate of reaction

katrin2010 [14]

Answer:Increasing the temperature increases reaction rates because of the disproportionately large increase in the number of high energy collisions. It is only these collisions (possessing at least the activation energy for the reaction) which result in a reaction.

Explanation:

5 0

3 years ago

A hypothetical wave has 4.6 J of energy. What is its hypothetical, approximate frequency?

Mariulka [41]

Answer:

6.94 × 10^33Hz

Explanation:

E = hf

Where;

E = Energy of wave (J)

h = Planck's constant (6.626 × 10^-34J/s)

f = frequency (Hz)

According to the information provided in this question, the hypothetical energy of the wave is 4.6J

Hence, using E = hf

4.6 = 6.626 × 10^-34 × f

f = 4.6 / 6.626 × 10^-34

f = 0.694 × 10^34

f = 6.94 × 10^33Hz

3 0

3 years ago