Answer:
THE SOUND TRAVELS FASTER IN SOLIDS BECAUSE ITS MOLECULES ARE CLOSE TO EACH OTHER WHILE LIQUIDS MOLECULES ARE NOT TIGHT AS OF SOLID AND IN GAS THE MOLECULES ARE FREE
pH of buffer can be calculated as:
pH=pKa+log[salt]/[Acid]
As ka = 4.58 x 10-4
Concentration of [Salt] that is NO2(-1)=0.380M
Concentration of [Acid] that is HNO2=0.500M
So, pH= -log(4.58*10^-4)+log((0.380)/0.500))
=3.21
So pH of solution will be 3.21
Answer:
6. 7870 kg/m³ (3 s.f.)
7. 33.4 g (3 s.f.)
8. 12600 kg/m³ (3 s.f.)
Explanation:
6. The SI unit for density is kg/m³. Thus convert the mass to Kg and volume to m³ first.
1 kg= 1000g
1m³= 1 ×10⁶ cm³
Mass of iron bar
= 64.2g
= 64.2 ÷1000 kg
= 0.0642 kg
Volume of iron bar
= 8.16 cm³
= 8.16 ÷ 10⁶
Density of iron bar
= 7870 kg/m³ (3 s.f.)
7.
Mass
= 1.16 ×28.8
= 33.408 g
= 33.4 g (3 s.f.)
8. Volume of brick
= 12 cm³
Mass of brick
= 151 g
= 151 ÷ 1000 kg
= 0.151 kg
Density of brick
= mass ÷ volume
(3 s.f.)
<u>Given:</u>
Calculated density values-
Aluminum = 2.7 g/cm3
Copper = 9.0 g/cm3
Iron = 7.9 g/cm3
Titanium = 4.8 g/cm3
Unknown sample mass = 9.5 g
Sample volume = 2.1 cm3
<u>To determine:</u>
The identity of the unknown sample
<u>Explanation:</u>
'Density' is a physical parameter which can be used to identify the nature of the unknown substance.
Density = Mass/Volume
For the unknown sample
Density = 9.5 g/2.1 cm3 = 4.52 g/cm3
This matches closely with the calculated density of titanium
Ans: The unknown substance is made of titanium
