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3 years ago

Help me please I really need this tomorrow

Chemistry

2 answers:

Elena L [17]3 years ago

8 0

Answer:

answers:

1.b

2.d

3.b

4. c

5.c

6.d

7.c

Explanation:

I think this is the correct answer pls mark brainliest and like..

Vesna [10]3 years ago

7 0

19. place moth balls in the closet and observe after several days.

20. whenever wax or a candle burns it turns from solid to liquid but again at room temperature it turns to solid

21. evaporation, condensation, precipitation

22. it produces new substances

23. vinegar Bubbles when baking soda is added.

24. steam

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A 4.36-g sample of an unknown alkali metal hydroxide is dissolved in 100.0 mL of water. An acid-base indicator is added, and the

BARSIC [14]

Answer:

Rb+

Explanation:

Since they are telling us that the equivalence point was reached after 17.0 mL of 2.5 M HCl were added , we can calculate the number of moles of HCl which neutralized our unknown hydroxide.

Now all the choices for the metal cation are monovalent, therefore the general formula for our unknown is XOH and we know the reaction is 1 equivalent acid to 1 equivalent base. Thus we have the number of moles, n, of XOH and from the relation n = M/MW we can calculate the molecular weight of XOH.

Thus our calculations are:

V = 17.0 mL x 1 L / 1000 mL = 0.017 L

2.5 M HCl x 0.017 L = 2.5 mol/ L x 0.017 L = 0.0425 mol

0.0425 mol = 4.36 g/ MW XOH

MW of XOH = (atomic weight of X + 16 + 1)

so solving the above equation we get:

0.0425 = 4.36 / (X + 17 )

0.7225 +0.0425X = 4.36

0.0425X = 4.36 -0.7225 = 3.6375

X = 3.6375/0.0425 = 85.59

The unknown alkali is Rb which has an atomic weight of 85.47 g/mol

6 0

4 years ago

β‑Galactosidase (β‑gal) is a hydrolase enzyme that catalyzes the hydrolysis of β‑galactosides into monosaccharides. A 0.387 g sa

gtnhenbr [62]

Answer:

The molar mass of unknown β‑Galactosidaseis 116,352.97 g/mol.

Explanation:

To calculate the concentration of solute, we use the equation for osmotic pressure, which is:

$\pi=icRT$

where,

$\pi$ = osmotic pressure of the solution = 0.602 mbar = 0.000602 bar

0.000602 bar = 0.000594 atm

(1 atm = 1.01325 bar)

i = Van't hoff factor = 1 (for non-electrolytes)

c = concentration of solute = ?

R = Gas constant = $0.0820\text{ L atm }mol^{-1}K^{-1}$

T = temperature of the solution = $25^oC=[273.15 +25]=298.15 K$

Putting values in above equation, we get:

$0.000594 atm=1\times c\times 0.0821\text{ L.atm }mol^{-1}K^{-1}\times 298.15 K\\\\c=2.4278\times 10^{-5} mol/L$

The concentration of solute is $2.4278\times 10^{-5} mol/L$

Volume of the solution = V =0.137 L

Moles of β‑Galactosidase = n

$C=\frac{n}{V(L)}$

$n=2.4278\times 10^{-5} mol/L\times 0.137 L$

$n=3.3261\times 10^{-6} mol$

To calculate the molecular mass of solute, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Moles of β‑Galactosidase = $3.3261\times 10^{-6} mol$

Given mass of β‑Galactosidase= 0.387 g

Putting values in above equation, we get:

$3.3261\times 10^{-6} mol =\frac{0.387 g}{\text{Molar mass of solute}}\\\\\text{Molar mass of solute}=116,352.97 g/mol$

Hence, the molar mass of unknown β‑Galactosidaseis 116,352.97 g/mol.

3 0

3 years ago

The diagram below shows a longitudinal wave at one instant in its motion. Each oval represents a particle acted on by the ener t

Anton [14]

Answer:

the first line

Explanation:

A rarefaction is a region in a longitudinal wave where the particles are furthest apart. ... The region where the medium is compressed is known as a compression and the region where the medium is spread out is known as a rarefaction.

use this picture as a reference:

8 0

3 years ago

Read 2 more answers

Which type of molecule is propanol? <br> A. Alcohol <br> B. Aldehyde <br>C. Ketone <br>D. Amine

snow_lady [41]

Answer:

Explanation:

Propanal is an organic compound with the formula CH3CH2CHO. Aldehyde is colorless, flammable and a slightly fruity odor.

8 0

3 years ago

5. Extend your thinking: What strategies did you use to hunt for moths?

Sonja [21]

Answer: There are many strategies used to hunt and kill moths. I’ll tell you my way of hunting and killing moths.

Step-By-Step Explanation:
Morning and Afternoon: First, get a sticky trap. You can get it at Target or Walmart. Cover it with moth pheromones or anything you know that can attract the moths. The sticky trap, will stick them to the trap and will eventually die after no being able to escape for a long time.
Nighttime: Buy or Get a lamp and turn it on. This will attract lots of moths and it will help you see them. Then, spray insecticide or insect repellent at the. Lastly, they should die.
Tip: If things get too out of hand with a huge swarm of moths, then call pest control and they will surely get rid of them for you!

8 0

3 years ago