5. What are the two types of pure substances ?

I need help with number 3. is the answer 1,2,3,or4

lubasha [3.4K]

Answer:

1 and 4

Explanation:

in both pictures the temperature is cooling down

8 0

3 years ago

Briefly describe how a potentiometric pHmeter works. (Hint: Describe how the pH meter measures the amount of H+ or OH- ions in a

KengaRu [80]

Answer:

Indicators show changes in the pH of a solution

Explanation:

A pH meter is an instrument that measures the hydrogen-ion activity in aqueous solutions, indicating the acidity or alkalinity of the solution expressed as pH .The pH meter measures the difference in electrical potential between a pH electrode and a reference electrode, hence the pH meter is sometimes referred to as a potentiometric pH meter. Potentiometric pH meters measure the voltage between two electrodes and display the result converted into the corresponding pH value. The instrument comprises of a simple electronic amplifier and a pair of electrodes, or alternatively a combination electrode, and some form of display calibrated in pH units. It usually has a glass electrode and a reference electrode, or a combination electrode. The electrodes, or probes, are inserted into the solution to be tested.

Organic indicators are chemical species that change their colour in response to changes in the pH of the solution. This implies that the anionic and protonated forms of the indicator possess different colours. Hence the colour changes in acidic, basic and neutral solutions. The images attached indicate the colour changes in phenolphthalein and methyl orange in acidic and basic media accordingly.

4 0

2 years ago

What system of units is used by only a small number of countries in the world, including the U.S.?

Aleks04 [339]

Answer:

The correct answer is the imperial system.

Explanation:

Only three countries in the world, that is, the United States, Myanmar, and Liberia use the imperial system. These include measurements in the form of inches, ounces, Fahrenheit, and feet. In the imperial system, the distances, height, weight, or area measurements are used eventually that traced back to everyday items or parts of the body.

In comparison to other metric systems, the units used in the imperial system are not further differentiated easily into parts of hundreds or thousands, and are thus, regarded of less use in comparison to other metric systems by some. The real follower of the imperial system at present in the world is the United States.

4 0

2 years ago

You need to produce a buffer solution that has a pH of 5.31. You already have a solution that contains 10. mmol (millimoles) of

Karolina [17]

Answer:

37 mmol of acetate need to add to this solution.

Explanation:

Acetic acid is an weak acid. According to Henderson-Hasselbalch equation for a buffer consist of weak acid (acetic acid) and its conjugate base (acetate)-

$pH=pK_{a}(acetic acid)+log[\frac{mmol of CH_{3}COO^{-}}{mmol of CH_{3}COOH }]$

Here pH is 5.31, $pK_{a}$ (acetic acid) is 4.74 and number of mmol of acetic acid is 10 mmol.

Plug in all the values in the above equation:

$5.31=4.74+log[\frac{mmol of CH_{3}COO^{-}}{10}]$

or, mmol of $CH_{3}COO^{-}$ = 37

So 37 mmol of acetate need to add to this solution.

3 0

2 years ago

If you had excess chlorine, how many moles of of aluminum chloride could be produced from 19.0 g of aluminum?

SIZIF [17.4K]

The chemical reaction would be written as follows:

2Al + 3Cl2 = 2AlCl3

We are given the amount of aluminum to be used in the reaction. This will be the starting point of the calculations. We do as follows:

19.0 g Al ( 1 mol / 29.98 g ) ( 2 mol AlCl3 / 2 mol Al ) = 0.63 mol AlCl3

5 0

2 years ago

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