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3 years ago

The number 40 in the name calcium-40 represents

Chemistry

2 answers:

strojnjashka [21]3 years ago

7 0

Answer:

A. the atomic number

Explanation:

It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth.

IgorC [24]3 years ago

4 0

A) the atomic number

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The partial pressure of N2 in a mixture of gases, where the total pressure is 1.50 atm, is 300. torr. What is the mole fraction

makvit [3.9K]

Answer:

The mole fraction of N₂ is 0.26.

Explanation:

The pressure exerted by a particular gas in a mixture is known as its partial pressure. So, Dalton's law states that the total pressure of a gas mixture is equal to the sum of the pressures that each gas would exert if it were alone:

PT = PA + PB

This relationship is due to the assumption that there are no attractive forces between the gases.

Dalton's partial pressure law can also be expressed in terms of the mole fraction of the gas in the mixture. The mole fraction is a dimensionless quantity that expresses the ratio of the number of moles of a component to the number of moles of all the components present.

So in a mixture of two or more gases, the partial pressure of gas A can be expressed as:

PA = XA * PT

In this case:

PA= PN₂= 300 torr
XA=XN₂= ?
PT= 1.50 atm= 1140 torr (being 1 atm= 760 torr)

Replacing:

300 torr= XN₂*1140 torr

Solving:

$X_{N_{2} } =\frac{300 torr}{1140 torr}$

XN₂= 0.26

The mole fraction of N₂ is 0.26.

6 0

2 years ago

Explain examples of a physical and chemical change of matter

monitta

HEY DEAR..

PHYSICAL CHANGE

Those Changes in which no new substances are formed are called physical changes. it is a temporary changes which can be reversed easily to form the original substance.

Example:- Melting of ice , Making a solution, Glowing of an electric bulb , freezing of water etc.

CHEMICAL CHANGE

Those changes in which new substances are formed are called chemical changes. it means it is permanent changes which are usually irreversible.

Example:- Burning of charcoal, fuels and cutting of trees, even digestion of food is in chemical change.

HOPE ITS HELPFULLL

BE BRAINLY.

6 0

3 years ago

*multiple choice*

galben [10]

1.95 or 2 is the molarity of a 45.3g sample of KNO3 (101g) dissolved in enough water to make a 0.225L solution.

The correct answer is option b

Explanation:

Data given:

mass of KN $O_{3}$ = 45.3 grams

volume = 0.225 litre

molarity =?

atomic mass of KNO3 = 101 grams/mole

molarity is calculated by using the formula:

molarity = $\frac{number of moles}{volume of the solution}$

first the number of moles present in the given mass is calculated as:

number of moles = $\frac{mass}{atomic mass of 1 mole}$

number of moles = $\frac{45.3}{101}$

0.44 moles of KNO3

Putting the values in the equation of molarity:

molarity = $\frac{0.44}{0.225}$

molarity = 1.95

It can be taken as 2.

The molarity of the potassium nitrate solution is 2.

7 0

2 years ago

An atom has three shells with 3 electrons in the last shell. This atom could be.....

Oksana_A [137]

Since the total amount of valence electrons is 3, it is in group 13 in the periodic table..therefore, it is specified as Boron.✅

4 0

2 years ago

Calculate the equilibrium constant for the reaction between fe2+(aq) and zn(s) under standard conditions at 25∘c.

Hatshy [7]

Following reaction occurs in the given electrochemical system:
$Fe^{2+} + Zn$ → Fe + $Zn^{2+}$
Thus, under standard conditions
E(0) = E(0) Fe2+/Fe - E(0) Zn2+/Zn
where, $E^{0}Fe2+/Fe$ = standard reduction potential of Fe2+/Fe = -0.44 v
$E^{0}Zn2+/Zn$ = standard reduction potential of Zn2+/Zn = -0.763 v

E(0) = 0.323 v
now, we know that, ΔG(0) =-nFE(0) ............... (1)
Also, Δ $G^{0} = -RTln(K) ............ (2)$

On equating and rearranging equation 1 and 2, we get
K = exp( $\frac{nFE(0)}{RT}$ )= exp ( $\frac{2X96500X0.323}{8.314X298}$ ) = 8.46 x $10^{10}$

7 0

2 years ago