Question

calculate the no of moles present in a solution containing 35 grams of sodium hydroxide presnt in 70 gm of water I NEED THE ANSWER STEP BY STEP THEN I WILL MAKE U BRAINLIEST

Answer 1

MOLES FROM VOLUME OF PURE LIQUID OR SOLID

There are two steps:

Multiply the volume by the density to get the mass.

Divide the mass by the molar mass to get the number of moles.

Example

How many moles are in 10.00 mL of acetic anhydride? The molar mass of acetic anhydride is 102.1 g/mol and its density is 1.080 g/mL?

Solution

The formula for density is

¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

∣

∣

∣

a

a

ρ

=

m

V

a

a

∣

∣

∣

−−−−−−−−−−−−

where

ρ

is the density,

m

is the mass, and

V

is the volume of the sample.

We can rearrange the formula to get

m

=

V

×

ρ

mass

=

10.00

mL

×

1.080 g

1

mL

=

10.80 g

n

=

10.80

g

×

1 mol

102.1

g

=

0.1058 mol

MOLES FROM VOLUME OF SOLUTION

Molarity is the number of moles of a substance in one litre of solution.

¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

∣

∣

∣

a

a

M

=

n

V

a

a

∣

∣

∣

−−−−−−−−−−−−

where

n

is the number of moles and

V

is the volume in litres.

We can rearrange this equation to get the number of moles:

n

=

M

×

V

Example

How many moles of

NaCl

are contained in 0.300 L of 0.400 mol/L

NaCl

solution?

Solution

n

=

0.300

L soln

×

0.400 mol NaCl

1

L soln

=

0.120 mol NaCl

Answer 2

The effects of climate change on South Asia are significant, and are expected to intensify as global temperatures rise due to climate change. In the 2017 edition of Germanwatch's Climate Risk Index, two countries in South Asia, Bangladesh and Pakistan ranked sixth and seventh respectively as the countries most affected by climate change in the period from 1996–2015, while India ranked fourth among the list of countries most affected by climate change in 2015.[1] The region, home to 1.947 billion people,[2] is one of the most vulnerable regions globally to a number of direct and indirect effects of climate change, including sea level rise, cyclonic activity, and changes in ambient temperature and precipitation patterns. Ongoing sea level rise has already submerged several low-lying islands in the Sundarbans region, displacing thousands of people.

Among the countries of South Asia, Bangladesh is likely to be the worst affected by climate change. This is owing to a combination of geographical factors, such as its flat, low-lying, and delta-exposed topography,[3] and socio-economic factors, including its high population density, levels of poverty, and dependence on agriculture.[4] Its sea level, temperature, and evaporation are increasing, and the changes in precipitation and cross-boundary river flows are already beginning to cause drainage congestion. There is a reduction in freshwater availability, disturbance of morphological processes, and a higher intensity of flooding.࿐