The elements in group 7a are known by what name? transition metals halogens alkali metals alkaline earth metals noble gases

What coefficient is missing in C2H4 + (?)O2 → 2CO2 + 2H2O?

Daniel [21]

Answer:

3

Explanation:

you must multiply everything out till everything is equal on both sides

7 0

3 years ago

The hydrogen-line emission spectrum includes a line at a wavelength of 434 nm. What is the energy of this radiation? (h= 6.626 x

Andrews [41]

Wavelength = 434nm = 434 x 10⁻⁹m
planck's constant = <span>h= 6.626 x 10 ⁻³⁴ J
E =?
by using the formula;
E = hc /</span>λ
value for c is 3 x 10⁸ m/s
E = (6.626 x 10 ⁻³⁴ J)(3 x 10⁸ m/s) / 434 x 10⁻⁹m
E = 1.9878 x 10⁻²⁵ / 434 x 10⁻⁹m
E = 4.58 x 10⁻¹⁹ joules

6 0

3 years ago

How are isotopes of the same chemical element alike? How are they different?

Stella [2.4K]

<u>Answer:</u> The atomic mass of these species is different and atomic number remains same.

<u>Explanation:</u>

Isotopes are the chemical species of the same element having different number of neutrons.

Atomic number is equal to the number of protons or electrons present in that element.

Atomic Number = Number of electrons = Number of protons

Atomic mass is defined as the sum of number of protons and neutrons contained in an atom.

Atomic Mass = Number of protons + Number of neutrons

For isotopes, as the number of neutrons differ, the atomic mass also differs.

For Example: Carbon has 3 naturally occurring isotopes: $_6^{12}\textrm{C},_6^{13}\textrm{C}\text{ and }_6^{14}\textrm{C}$ . The atomic number remains the same but atomic mass differs.

Hence, for isotopes, the atomic mass of these species is different and atomic number remains same.

6 0

3 years ago

Which half-reaction correctly shows the oxidation of iron

pishuonlain [190]

Answer:

What is the oxidation half reaction for iron?

The two elements involved, iron and chlorine, each change oxidation state; iron from +2 to +3, chlorine from 0 to -1. There are then effectively two half-reactions occurring. These changes can be represented in formulas by inserting appropriate electrons into each half-reaction: Fe2+ → Fe3+ + e.

Hope this helps..

8 0

3 years ago

A 50.00 g sample of an unknown metal is heated to 45.00°C. It is then placed in a coffee-cup calorimeter filled with water. The

V125BC [204]

Taking into account the definition of calorimetry, the specific heat of metal is 0.165 $\frac{cal}{gC}$ .

<h3>Definition of calorimetry</h3>

Calorimetry is the measurement and calculation of the amounts of heat exchanged by a body or a system.

Sensible heat is defined as the amount of heat that a body absorbs or releases without any changes in its physical state (phase change).

So, the equation that allows to calculate heat exchanges is:

Q = c× m× ΔT

where:

Q is the heat exchanged by a body of mass m.
C is the specific heat substance.
ΔT is the temperature variation.

<h3>Specific heat capacity of the metal</h3>

In this case, you know:

For metal:

Mass of metal = 50 g
Initial temperature of metal= 45 °C
Final temperature of metal= 11.08 ºC
Specific heat of metal= ?

For water:

Mass of water = 250 g
Initial temperature of water= 10 ºC
Final temperature of water= 11.08 ºC
Specific heat of water = 1.035 $\frac{cal}{gC}$

Replacing in the expression to calculate heat exchanges:

For metal: Qmetal= Specific heat of metal× 50 g× (11.08 C - 45 C)

For water: Qwater= 1.035 $\frac{cal}{gC}$ × 250 g× (11.08 C - 10 C)

If two isolated bodies or systems exchange energy in the form of heat, the quantity received by one of them is equal to the quantity transferred by the other body. That is, the total energy exchanged remains constant, it is conserved.

Then, the heat that the gold gives up will be equal to the heat that the water receives. Therefore:

- Qmetal = + Qwater

- Specific heat of metal× 50 g× (11.08 C - 45 C)= 1.035 $\frac{cal}{gC}$ × 250 g× (11.08 C - 10 C)

Solving:

- Specific heat of metal× 50 g× (-33.92 C)= 1.035 $\frac{cal}{gC}$ × 250 g× 1.08 C

Specific heat of metal× 1696 g×C= 279.45 cal

Specific heat of metal= $\frac{279.45 cal}{1696 gC}$