You need to find the frequency, and they have already given you the wavelength. And since you already know the speed of light, you can use formula (2) to answer this problem. Remember to convert the nano meters to meters because the speed of light is in meters. $(1 nm = 1.0 x 10^{-9} m)$

$v=c\lambda \\v= (3.00 \times 10^8 m/s)/(6.9\times 10^-7 m) \\v = 4.35 \times 10^{14} s^{-1}$

8 0

3 years ago

How many grams of KBr is required to prepare 100 mL of<br> 2.0 M KBr solution?

sesenic [268]

Answer:

23.8g

Explanation :

Convert 2.0M into mol using mol= concentration x volume

2.0M x 0.1L (convert 100mL to L since the units for M is mol/L)

= 0.2 mol

We can now find grams by using the molar mass of KBr

=119.023 g/mol (Found online) webqc.org

but can be be calculated by using the molecular weight of K and Br found on the periodic table

We can now calculate the grams by using grams=mol x molar mass

119.023g/mol x 0.2mol

= 23.8046 g

=23.8g (rounded to 1decimal place)

4 0

3 years ago