3. Calculate the number of nickel atoms in a 5-cent coin of mass 0.942g if it was made of an alloy consisting of 75% copper and 25% nickel

2.41x10²¹ atoms

Explanation:

mass of nickel that are present in the coin can be determined Using ( 25% nickel) with j mass of coin= 0.942g )

mass of nickel = (0.942g) × (25/100)

= 0.2355g of Nickel

We need to convert this " gram" into " moles"

Mole= mass/ molar mass

Molar mass= 58.69 g/mol

0.2355 g) / (58.69 g/mol)

= 0.004 mol

We need to convert the moles to

number of atoms.

Avogadro's number= 6.023x10²³ atoms/mol

(0.004 × 6.023x10²³ atoms/mol)

=2.41x10²¹ atoms

i just learnt this recently but i need to look through my notes again

35. a insulated cylinder of solid gold (k 310 kw/m-k) of radius v2 m and height 5 m is heated at one end until the temperature at each point in the cylinder is given by w(r, y, z) (30 z2)(2-(r2+ y2). determine the rate of heat flow across each horizontal disk given by z 1, z 2, and z 3, identifying which has the greatest rate of heat flow across it.

explanation: