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3 years ago

How many molecules of HBr are present in 42.5 grams of HBr

1 answer:

4 0

HBr molar mass is 80.9 g/mol
this means in 80.9 g - 1 mol of HBr
1 mol consists of 6.022 x 10²³ molecules of HBr
that means in 80.9 g HBr there are 6.022 x 10²³ molecules of HBr
therefore in 42.5 g of HBr there are 6.022 x 10²³/80.9 * 42.5
the number of HBr molecules are therefore - 3.16 x 10²³ HBr molecules

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Determine the pHpH of an HFHF solution of each of the following concentrations. In which cases can you not make the simplifying

PIT_PIT [208]

The question is incomplete, complete question is :

Determine the pH of an HF solution of each of the following concentrations. In which cases can you not make the simplifying assumption that x is small? ( $K_a$ for HF is $6.8\times 10^{-4}$ .)

[HF] = 0.280 M

Express your answer to two decimal places.

Answer:

The pH of an 0.280 M HF solution is 1.87.

Explanation:3

Initial concentration if HF = c = 0.280 M

Dissociation constant of the HF = $K_a=6.8\times 10^{-4}$

$HF\rightleftharpoons H^++F^-$

Initially

c 0 0

At equilibrium :

(c-x) x x

The expression of disassociation constant is given as:

$K_a=\frac{[H^+][F^-]}{[HF]}$

$K_a=\frac{x\times x}{(c-x)}$

$6.8\times 10^{-4}=\frac{x^2}{(0.280 M-x)}$

Solving for x, we get:

x = 0.01346 M

So, the concentration of hydrogen ion at equilibrium is :

$[H^+]=x=0.01346 M$

The pH of the solution is ;

$pH=-\log[H^+]=-\log[0.01346 M]=1.87$

The pH of an 0.280 M HF solution is 1.87.

6 0

3 years ago

How do moss leaves and fish differ? How are they the same?

Lapatulllka [165]

Moss leaves and fish are different in that, the moss leave is a producer, that is, it produces its own food through photosynthesis while the fish is a consumer, it feeds on foods that are not produced by it.
Both moss and fish are the same in the sense that both have cell as their basic unit of life, that is, they both possess cells.

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3 years ago

How did the Bohr model of the atom affect scientific thought?

Vadim26 [7]

Answer:

C. Scientists accepted the model at first but later rejected it.

Explanation:

Scientists accepted the model at first because it explained the hydrogen emission spectrum.

However, with the development of quantum mechanics, scientists had to modify the model (not reject it).

Electrons still had specific energies, but they no longer travelled in fixed orbits.

Instead, electrons had a probability of being found in a given region of space.

5 0

3 years ago

Read 2 more answers

Consider the following balanced equation. SiO2(s)+3C(s)→SiC(s)+2CO(g) Complete the following table, showing the appropriate numb

vlada-n [284]

Answer:

mol(SiO₂) mol(C) mol(SiC) mol(CO)

3 9 3 6

1 3 1 2

13 39 13 26

2.5 7.5 2.5 5.0

1.4 4.2 1.4 2.8

Explanation:

From the balanced equation:

SiO₂(s) + 3C(s) → SiC(s) + 2CO(g),

It is clear that 1.0 mole of SiO₂ reacts with 3.0 moles of C to produce 1.0 mole of SiC and 2.0 moles of CO.

We can complete the table of no. of moles of each component:

1. 9.0 moles of C:

We use the triple amount of C, so we multiply the others by 3.0.

So, it will be 3.0 moles of SiO₂ with 9.0 moles of C that produce 3.0 moles of SiC and 6.0 moles of CO.

2. 1.0 mole of SiO₂:

We use the same amount of SiO₂ as in the balnced equation, so the no. of moles of other components will be the same as in the balanced equation.

So, it will be 1.0 moles of SiO₂ with 3.0 moles of C that produce 1.0 moles of SiC and 2.0 moles of CO.

3. 26.0 moles of CO:

We use the amount of CO higher by 13 times than that in the balanced equation, so we multiply the others by 13.0.

So, it will be 13.0 moles of SiO₂ with 39.0 moles of C that produce 13.0 moles of SiC and 26.0 moles of CO.

4. 7.5 moles of C:

We use the amount of C higher by 2.5 times than that in the balanced equation, so we multiply the others by 2.5.

So, it will be 2.5 moles of SiO₂ with 7.5 moles of C that produce 2.5 moles of SiC and 5.0 moles of CO.

5. 1.4 moles of SiO₂:

We use the amount of SiO₂ higher by 1.4 times than that in the balanced equation, so we multiply the others by 1.4.

So, it will be 1.4 moles of SiO₂ with 4.2 moles of C that produce 1.4 moles of SiC and 2.8 moles of CO.

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3 years ago

bottle contains 425 mL of insulin at a concentration of 50.0 mg/mL . What is the total mass of insulin in the bottle?

Ulleksa [173]

Hey there!

C = m
------
V

50.0 mg/mL = mass
---------------
425 mL

mass = 50.0 * 425

mass => 21250 mg

3 0

3 years ago