Question

An unknown mass of each substance, initially at 21.0 ∘C, absorbs 1950 J of heat. The final temperature is recorded. Find the mass of each substance.

a. Pyrex glass (Tf= 55.8 ∘C)

b. sand (Tf= 62.3 ∘C)

c. ethanol (Tf= 44.5 ∘C)

d. water (Tf= 32.0 ∘C)

Answer 1

Mass of each substance :-

a.

Q = m c_{Pyrex glass} ΔT

1950 J = m (0.84 kJ/kg K) (55.8 – 21.0)K

m = (1950 J) / {(0.84 kJ/kg K) (34.8 K)}

m = 66.707 g

b.

Q = m c_sand ΔT

1950 J = m (830 J/kg°C) (62.3 – 21.0) °C

m = (1950 J) / {(830J/ kg °C) (41.3 °C)}

m = 1950 / 34279 kg

m = 56.886 g

c.

Q = m c_ethanol ΔT

1950 J = m (2.44 J.g^-1K^-1) (44.5 - 21.0) K

m = (1950 J) / {(2.44 J.g^-1K^-1) (23.5 K)}

m = 1950 / 57.34 g

m = 34 g

d.

Q = m c_water ΔT

1950 J = m (4.184 J.g^-1K^-1) (32 - 21.0) K

m = (1950 J) / {(4.184 J.g^-1K^-1) (11 K)}

m = 1950 / 46.024 g

m = 42.369 g