If you had this equation: x(0.5)(320) = (1.2)(48)(325)

1. The atomic number is equal to the number of protons in the nucleus, and the mass number is equal to the number of protons and neutros in the nucleus.

Therefore, to find the number of neutrons we must do mass number - atomic number, which equals 54.

Answer 1: a. 54

2. Atoms of a same element that have a different number of neutrons in the nucleus are called isotopes of an element.

Answer 2: d. Isotopes

3. Potassium has an electron configuration of $[Ar] 4s^{1}$ , meaning that the first 3 shells are full, and that the last shell (4th one) has only 1 electron.

Answer 3: c. Shells 1, 2 and 3 are full and shell 4 has one electron.

4. An atomic bond isn't a specific bond, it's just a term. Polar covalent and non-polar covalent bonds are strong bonds, which leaves us with the hydrogen bonds, which are indeed the weakest bonds out there.

Answer 4: a. Hydrogen bond

Hope it helped,

BiologiaMagister

5 0

4 years ago

26.9 g of solid lithium is combined with 20.0 grams of nitrogen gas. .

SOVA2 [1]

Answer:

The theoretical yield of

Li

3

N

is

20.9 g

.

Explanation:

Balanced Equation

6Li(s)

+

N

2

(

g

)

→

2Li

3

N(s)

In order to determine the theoretical yield, we must first find the limiting reactant (reagent), which will determine the greatest possible amount of product that can be produced.

Molar Masses

Li

:

6.941 g/mol

N

2

:

(

2

×

14.007

g/mol

)

=

28.014 g/mol

Li

3

N

:

(

3

×

6.941

g/mol Li

)

+

(

1

×

14.007

g/mol N

)

=

34.83 g/mol Li

3

N

Limiting Reactant

Divide the mass of each reactant by its molar mass, then multiply times the mole ratio from the balanced equation with the product on top and the reactant on bottom, then multiply times the molar mass of

Li

3

N

.

Lithium

12.5

g Li

×

1

mol Li

6.941

g Li

×

2

mol Li

3

N

6

mol Li

×

34.83

g Li

3

N

1

mol Li

3

N

=

20.9 g Li

3

N

Nitrogen Gas

34.1

g N

2

×

1

mol N

2

28.014

g N

2

×

2

mol Li

3

N

1

mol N

2

×

34.83

g Li

3

N

1

mol Li

3

N

=

84.8 g Li

3

N

Lithium produces less lithium nitride than nitrogen gas. Therefore, the limiting reactant is lithium, and the theoretical yield of lithium nitride is

20.9 g

.

Explanation:

6 0

3 years ago

In a coffee-cup calorimeter, 150.0 mL of 0.50 M HCl is added to 50.0 mL of 1.00 M NaOH to make 200.0 g solution at an initial te

Zigmanuir [339]

Answer:

51.54°C the final temperature of the calorimeter contents.

Explanation:

$HCl+NaOH\rightarrow H_2O+NaCl,\Delta H=-56 kJ/mol$

$moles=Molarity\times Volume (L)$

Molarity of HCl= 0.50 M

Volume of HCl= 150.0 mL = 0.150 L

Moles of HCl= n

$n=0.50 M\times 0.150 L=0.075 mol$

Molarity of NaOH= 1.00 M

Volume of NaOH= 50.0 mL = 0.050 L

Moles of NaOH= n'

$n'=1.00 M\times 0.050 L=0.050 mol$

Since moles of NaOH are less than than moles of HCl. so energy release will be for neutralization of 0.050 moles of naOH by 0.050 moles of HCl.

n = 0.050

$-56 kJ/mol=-\frac{Q}{n}$

$Q=56 kJ/mol\times 0.050 kJ/mol=2.8 kJ=2800 J$

(1 kJ= 1000 J)

The energy change released during the reaction = 2800 J

Volume of solution = 150.0 mL + 50.0 mL = 200.0 mL

Density of the solution (water) = 1.00g/mL

Mass of the solution , m= 200 mL × 1.00 g/mL = 200 g

Now , calculate the final temperature by the solution from :

$q=mc\times (T_{final}-T_{initial})$

where,

q = heat gained = 2800 J

c = specific heat of solution = $4.184 J/^oC$

$T_{final}$ = final temperature = $?$

$T_{initial}$ = initial temperature = $48.2^oC$

Now put all the given values in the above formula, we get:

$2800 J=200.0 g\times 4.184 J/^oC\times (T_{final}-48.2)^oC$

$T_{final}= 51.54^oC$

51.54°C the final temperature of the calorimeter contents.

7 0

3 years ago