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4 years ago

Which one of these is not a pathogen?

1 answer:

5 0

B, plant

A pathogen is a bacterium, virus, or other microorganisms that can cause disease. A plant does cause a disease

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Starting with 0.250L of a buffer solution containing 0.250 M benzoic acid (C 6H 5COOH) and 0.20 M sodium benzoate (C 6H 5COONa),

Zigmanuir [339]

Answer:

pH = 4.05

Explanation:

The pH of the benzoic buffer can be determined using H-H equation:

pH = pKa + log [A⁻] / [HA]

Where pKa is -logKa = 4.187

pH = 4.187 + log [Sodium Benzoate] / [Benzoic Acid]

Where [] can be understood as moles of each specie.

Thus, to find pH of the buffer we need to calculate moles of benzoic acid and sodium benzoate.

Initial moles:

Initial moles of benzoic acid and sodium benzoate are:

Acid: 250mL = 0.250L ₓ (0.250 moles / L) = 0.0625 moles of benzoic acid

Benzoate : 250mL = 0.20L ₓ (0.250 moles / L) = 0.050 moles of sodium benzoate

Moles after reaction:

Now, 0.0250L×(0.100mol/L) = 0.0025 moles of HCl are added to the buffer reacting with sodium benzoate, C₆H₅COONa, producing more benzoic acid, as follows:

HCl + C₆H₅COONa → C₆H₅COOH + NaCl

That means after reaction moles of both species are:

Benzoic acid: 0.0625 mol + 0.0025mol (Moles produced) = 0.065 moles

Sodium Benzoate: 0.050mol - 0.0025mol (Moles that react) = 0.0475 moles

Replacing in H-H equation:

pH = 4.187 + log [0.0475] / [0.065]

pH = 4.05

5 0

4 years ago

Which of the following is a physical change?

MissTica

Answer:

boiling water

Explanation:

6 0

3 years ago

The pH scale for acidity is defined by pH=−log10[H⁺] where [H⁺]is the concentration of hydrogen ions measured in moles per liter

masha68 [24]

Answer:

5.62 * 10^-13 moles per liter

Explanation:

The pH of a solution is the negative logarithm to base 10 of the concentration of hydrogen ions. What we simply do here is to input the information in the question into the equation:

pH=−log10[H⁺]

Here we know the pH but we do not know the concentration of the hydrogen ions.

12.25 = -log [H+]

log[H+] = -12.25

[H+] = 10^-12.25

[H+] = 5.62 * 10^-13 moles per liter

7 0

3 years ago

Determine the theoretical yield of HCl if 60.0 g of BC13 and 37.5 g of H20 are reacted according to the following balanced react

Pie

Answer : The theoretical yield of HCl is, 56.1735 grams

Explanation : Given,

Mass of $BCl_3$ = 60 g

Mass of $H_2O$ = 37.5 g

Molar mass of $BCl_3$ = 117 g/mole

Molar mass of $H_2O$ = 18 g/mole

Molar mass of $HCl$ = 36.5 g/mole

First we have to calculate the moles of $BCl_3$ and $H_2O$ .

$\text{Moles of }BCl_3=\frac{\text{Mass of }BCl_3}{\text{Molar mass of }BCl_3}=\frac{60g}{117g/mole}=0.513moles$

$\text{Moles of }H_2O=\frac{\text{Mass of }H_2O}{\text{Molar mass of }H_2O}=\frac{37.5g}{18g/mole}=2.083moles$

Now we have to calculate the limiting and excess reagent.

The balanced chemical reaction is,

$BCl_3(g)+3H_2O(l)\rightarrow H_3BO_3(s)+3HCl(g)$

From the balanced reaction we conclude that

As, 1 mole of $BCl_3$ react with 3 mole of $H_2O$

So, 0.513 moles of $BCl_3$ react with $3\times 0.513=1.539$ moles of $H_2O$

From this we conclude that, $H_2O$ is an excess reagent because the given moles are greater than the required moles and $BCl_3$ is a limiting reagent and it limits the formation of product.

Now we have to calculate the moles of $HCl$ .

As, 1 mole of $BCl_3$ react to give 3 moles of $HCl$

So, 0.513 moles of $BCl_3$ react to give $3\times 0.513=1.539$ moles of $HCl$

Now we have to calculate the mass of $HCl$ .

$\text{Mass of }HCl=\text{Moles of }HCl\times \text{Molar mass of }HCl$

$\text{Mass of }HCl=(1.539mole)\times (36.5g/mole)=56.1735g$

Therefore, the theoretical yield of HCl is, 56.1735 grams

7 0

3 years ago

Which property can be used to tell gold and pyrite apart?

zubka84 [21]

Answer:

D. Malleability

Explanation:

Gold is made up of the element Au and it is a metal.

Pyrite is iron sulfide and it is a non-metal.

They have very similar appearance to such an extent that pyrite is widely called the fool's gold.
To distinguish between the two, we simply explore their metallic properties.
Gold is malleable. Pyrite is not. It will crumble under pressure.

6 0

3 years ago