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3 years ago

I need more help with science again

Chemistry

2 answers:

Sloan [31]3 years ago

5 0

Membranes are barriers and “gatekeepers”, they only let certain molecules pass through them.

they also transport nutrients to the cell

Rina8888 [55]3 years ago

3 0

Cell membrane : decides what enters and leaves, it also decides which proteins come in and out
passive transport : passive transport uses energy and i’m pretty sure it’s a transport that allows only some proteins to go through such as proteins

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A volume of 25cm3 of a carbonate solution of concentration 0.2mol dm-3 was neutralized by 20 cm3 of acid of concentration 0.5 mo

Galina-37 [17]

Answer: 1 mol of carbonate to 2 mol of acid

Explanation:

To calculate the number of moles for given molarity, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}\times 1000}{\text{Volume of solution in ml}}$

a) $\text{Moles of carbonate}=\frac{0.2moldm^{-3}\times 25cm^3}{1000}=0.005mol$

b) $\text{Moles of acid}=\frac{0.5moldm^{-3}\times 20cm^3}{1000}=0.01mol$

Thus the mole ratio of carbonate to acid is = $\frac{0.005}{0.01}=\frac{1}{2}$

7 0

3 years ago

According to the phase diagram for water, how is the state of water determined?

joja [24]

Explanation:

From the attached phase diagram, one can easily make out the phase in which water exists. Matter generally exists in three physical states which are solid, liquid and gas. Water is a unique compound that can exists in these three states at a given temperature and pressure.

From the attached phase diagram,

point O is the triple point where the three phases of pure substance co-exists.
The areas between the curves points at a single phase of matter. Y is a water vapor.
The lines on the curve denotes two equilibrium phases. For example; X is a phase contain ice and melt water.

Learn more:

brainly.com/question/1612862

#learnwithBrainly

3 0

3 years ago

Read 2 more answers

The rate law for the decomposition of phosphine () is It takes 135. s for 1.00 M to decrease to 0.250 M. How much time is requir

vova2212 [387]

Answer:

189.71 secs

Explanation:

We know that decomposition is a first order reaction;

So;

ln[A] = ln[A]o - kt

But;

[A]o = 1.00 M

[A] = 0.250 M

t =135 s

Hence;

ln[A] - ln[A]o = kt

k = ln[A] - ln[A]o/t

k = ln(1) - ln(0.250)/135

k =0 - (-1.386)/135

k = 1.386/135

k= 0.01

So time taken now will be;

ln[A] - ln[A]o = kt

t = ln[A] - ln[A]o/k

t = ln (3) - ln(0.450)/0.01

t = 1.0986 - (-0.7985)/0.01

t = 1.0986 + 0.7985/0.01

t = 189.71 secs

8 0

3 years ago

2.70g of Zn (s) reacts with 50.0 mL of 1.00 M HCl solution to produce hydrogen gas according to the reaction. (R = 0.08206 L·atm

Anika [276]

Answer:

a. 0.0413 moles Zn

b. 0.0500 moles HCl

c. HCl is the limiting reactant

d. 0.0250 moles H₂

e. V = 0.56L

Explanation:

The reaction of Zn(s) with HCl is:

Zn(s) + 2HCl (aq) → ZnCl₂ (aq) + H₂(g)

Where 1 mole of Zn reacts with 2 moles of HCl.

a) To convert mass in grams to moles of a substance you need to use molar mass (Molar mass Zn: 65.38g/mol), thus:

2.70g Zn × (1mol / 65.38g) = 0.0413moles of Zn

b. Now, when you have a solution in molarity (Moles / L), you can know the moles of a volume of solution, thus:

Moles HCl:

50.0mL = 0.0500L × (1.00mol / L) = 0.0500 moles HCl

c. The limiting reactant is founded by using the chemical reaction as follows:

For a complete reaction of 0.0500 moles HCl you need:

0.0500 moles HCl × (1 mole Zn / 2 moles HCl) = 0.0250 moles Zn

As you have 0.0413 moles of Zn, and you need just 0.0250 moles for the complete reaction, Zn is the exces reactant and HCl is the limiting reactant

d.As HCl is limiting reactant and 2 moles of HCl react with 1 mole of H₂, moles of hydrogen formed are:

0.0500 moles HCl × (1 mole H₂ / 2 moles HCl) = 0.0250 moles H₂

e. Using PV = nRT, you can find volume of gas, thus:

PV = nRT

V = nRT / P

Where P is pressure 1atm at STP, n are moles, R is gas consant 0.08206Latm/molK and T is absolute temperature 273.15K at STP.

V = 0.0250molesₓ0.082atmL/molKₓ273.15K / 1atm

V = 0.56L

3 0

3 years ago

17. An industrially important element contains

likoan [24]

Answer:

Iron (Fe)

Explanation:

The number of electrons (-) is usually the same as the number of protons (+) in the atom of the element (unless it is an ion).

The element described has 26 electrons, so we can assume that it has 26 protons as well. The number of protons in an atom is the atomic number of element that the atom is.

Element 26 on the PTE is Iron (Fe), which does rust (oxidation) in air and water.

8 0

3 years ago