Question

which if the followings has the shortest length

400pm

4.0 x10^-4m

4.0 x 10^-10cm

4.0 nm

how many atoms are in 236 grams of arsenic?

0.0695

9.51 x 10^22

4.19 x 10^22

1.90 x 10^24

7.80 x 10^24

which of the following is iconic compound?

kcl

co2

no2

pcl3

Answer 1

1)

(a) 1pm = 10^-12m.

Therfore, 400 pm = 4 $\times$ 10^-10 m.

(b) 4.0 $\times$ 10^-4m

(c) 4.0 $\times$ 10^-10cm = 4.0 $\times$ 10^-12cm.

(d) 1nm = 10^-9m.

Therfore, 4.0 nm= 4.0$\times$​​​​​​10^-9m.

Therefore, option (c) is the shortest of all.

2)

Arsenic atomic weight = 74.92 g/mol.

Therefore, no.of moles of arsenic present= 236 g / 74.92 g/mol = 3.15 mol.

And 1 mole of aresnic contains 6.023$\times$ 10²³ atoms of arsenic.

Therefore, total no.of arsenic atoms present in 236 g of arsenic = 3.15$\times$ 6.023$\times$ 10²³=1.90 $\times$ 10²⁴.

3)

An ionic compound is the compound in which the atoms are ions and are held by the electrostatic force of attraction.Like there are positive and negative charges are held by balanced electrostatic forces.

Whereas in covalent compounds, the atoms are hepd together by covalent bonds like the sigma bond, pi bond which we study, where the orbitals overlap 2ith each other.

In the given options, only KCl is the ionic compound and the others are covalent.