Correct answer only !

the hum (sound wave) you may have heard from a transformer has a frequency of about 100 hz and a wavelength of 3.4 m. how fast does the hum travel?

remember that v= λ ∙ f

Did you see that formula at the bottom of the question ? The one that says. V = L x f ?

That's where you can stick the numbers that the question also gives you.

L = 3.4 m

f = 100 Hz

Puttum in the formula and then it says

V = (3.4 m) (100 Hz)

The question wants to know what ' v ' is.

Do that one multiplication and you'll have it.

It's 340 m/s.

Surprise surprise ! It's the speed of sound in air.

  the grams     of oxygen gas   that can be produced     is 20.6   grams of o₂

calculation

2liclo₃ →   2 licl + 3 o₂

step 1:   find the moles of liclo₃

moles = mass÷ molar mass

from periodic table the molar mass of liclo₃ =6.9 +35.5   +(16 x3) =90.4 g/mol

moles=38.7 g÷90.4 g/mol=0.4281   moles

step 2:   use the   mole ratio   to calculate the moles of o2

from equation above, liclo₃: o₂   is 2: 3  

therefore the moles of   o₂=0.4281 moles x3/2 =0.6422   moles

step 3: find mass   of o₂

mass= moles x molar mass

from periodic table the   molar mass of   o₂ = 16 x2= 32 g/mol

mass=0.6422   moles   x   32 g/mol = 20.6 grams of o₂