Determine the molecular and empirical formulas for the substance shown in the ball-and-stick model below.

The following table lists the speed of sound in various materials. Use this table to answer the question.

Lynna [10]

Answer: Time taken by a sound impulse to travel through an aluminum rod 25 kilometers long is 4.9 seconds.

Solution:

Length of aluminium rod = 25 km = 25000 m (1 km=1000 m)

Time taken by sound to travel through aluminium = 5100 m/s (from the table given)

$speed=\frac{distance}{time}=\frac{25000 m}{\text{time taken}}$

time taken = $\frac{distance}{speed}=\frac{25000 m}{5100 m/s}=4.9019 seconds\approx 4.9 seconds$

Hence, the correct option is 4.9 seconds.

4 0

3 years ago

Read 2 more answers

Which half-reaction correctly represents reduction?

Neko [114]

Answer: B. Ca2+ + 2e- ---------> Ca

Explanation:

Reduction involves the gaining of electrons as well as a decrease in the oxidation state of the atom or ion.

In this case; Ca2+ gains two electrons and the oxidation state is reduced from +2 to 0.

Ca2+ + 2e- ---------> Ca

5 0

3 years ago

50 POINTS!!!

lesya692 [45]

The answer is: K is more reactive than Ca because K has to lose only one electron to complete its outermost shell.

Potassium is a chemical element with atomic number 19 (number of electrons is 19).

Electron configuration of potassium is: ₁₉K 1s²2s²2p⁶3s²3p⁶4s¹.

Potassium is the alkali metal and has a single valence electron in the outer electron shell.

Periodic law is the arrangement of the elements in order of increasing atomic number.

For example all alkaline metals (I group of periodic table, Na, K, Cs...) loose one electron in chemical reaction and react vigorously with water.

Reactivity series is an empirical progression of a series of metals, arranged by their reactivity from highest to lowest (alkaline metals have highest reactivity and Noble metals lowest reactivity).

The ionization energy (Ei) is the minimum amount of energy required to remove the valence electron, when element lose electrons, oxidation number of element grows (oxidation process).

Alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons (one electron, earth alkaline metals (right next to alkaline metals) have higher ionization energy than alkaline metals, because they have two valence electrons.

7 0

4 years ago

Predict the mass of iron (III) sulfide produced when 3.0 g of iron filings react completely with 2.5 g of yellow sulfur solid, S

777dan777 [17]

1) Chemical equation

16Fe(s) + 3S8(s) ---> 8Fe2S3

2) Molar ratios:

16 mol Fe : 3 mole S8 : 8 mol Fe2S3

3) Convert masses in grams to number of moles

number of moles = mass in grams / molar mass

a) iron, Fe

mass = 3.0 g
atomic mass = 55.845 g/mol

=> number of moles of Fe = 3.0g / 55.845 g/mol = 0.0537 mol

b) Sulfur, S8

mass = 2.5 g
molar mass = 8*32.065 g/mol = 256.52 g/mol

=> number of moles of S8 = 2.5g / 256.52 g/mol = 0.009746 mol

4) Limiting reactant

Theoretical ratio                           actual ratio

16 mol Fe / 3 mol S8                 0.0537 mol Fe / 0.009746 mol S8

5.33                                               5.50

So, there is a little bit more Fe than the theoretical needed to react all the S8, which means the S8 is the limiting reactant.

5) Calculate the number of moles of iron (III) produced with 2.5 g (0.009746 moles) of S8

3moles S8 / 8 moles Fe2S3 = 0.009746 moles S8 / x

=> x = 0.009746 * 8 / 3 moles Fe2S3 = 0.026 moles Fe2S3

6) Convert 0.026 moles Fe2S3 into grams

mass in grams = number of moles * molar mass

molar mass of Fe2S3 = 207.9 g/mol

mass = 0.026 mol * 207.9 g/mol = 5.40 g

7) Answer: option D)

3 0

3 years ago

Read 2 more answers

Calculate the number of grams of sodium chloride in the solution. (Hint: Remember that sodium chloride is a strong electrolyte.)

creativ13 [48]

The question is incomplete, here is the complete question:

A solution contains 0.115 mol $H_2O$ and an unknown number of moles of sodium chloride. The vapor pressure of the solution at 30°C is 25.7 torr. The vapor pressure of pure water at this temperature is 31.8 torr. Calculate the number of grams of sodium chloride in the solution. (Hint: Remember that sodium chloride is a strong electrolyte.)