Answer: 0.028 grams
Explanation:
Depression in freezing point :
Formula used for lowering in freezing point is,
or,
where,
= change in freezing point
= freezing point constant (for benzene} =
m = molality
Putting in the values we get:
0.028 grams of DDT (solute) must be dissolved in 209.0 grams of benzene to reduce the freezing point by 0.400°C.
The number of years required for 1/4 cobalt-60 to remain after decay is calculated as follows
after one half life 1/2 of the original mass isotope remains
after another half life 1/4 mass of original mass remains
therefore if one half life is 5.3 years then the years required
= 2 x 5.3years = 10.6 years
Answer:
B
Explanation:
Dalton worked with mainly about the chemistry of atoms.
how do atoms combine to form various molecules.
—rather than the details of the physical, internal structure of atoms, although he never denied the possibility of atoms' having a substructure.
Answer:
The mass of board is 1.52 g.
Explanation:
Given data:
Density of wood = 0.487 g/cm³
Length of board = 3.21 cm
Width of board = 12.2 cm
Height of board = 0.80 mm (0.80/10=0.08 cm)
Mass of board = ?
Solution:
We know that density of an object is equal to the mass of substance divided by its volume. So we can calculate the mass from density formula.
Formula:
D = m/v
d = density
m = mass
v = volume
Now we will calculate the volume first.
V = length × width × height
V = 3.21 cm × 12.2 cm × 0.08 cm
V = 3.13cm³
Now we will calculate the mass.
D = m/v
0.487 g/cm³ = m/ 3.13 cm³
m = 0.487 g/cm³ × 3.13 cm³
m = 1.52 g
The mass of board is 1.52 g.