A helium balloon contains 0.46g off helium. how many moles of helium does it contain?

How did the work of louis pasteur help modern day medicine?

drek231 [11]

Pasteur showed that airborne microbes were the cause of disease. Pasteur built on the work of Edward Jenner and helped to develop more vaccines Pasteur’s career showed how conservative the medical establishment was at the time.

6 0

3 years ago

ammonia (NH3(g) Hf=-45.9 kJ/mol) reacts. with oxygen to produce nitrogen and water (H2O(g) Hf = -241.8 kJ/mol according to the e

kherson [118]

Answer:

ΔH°_rxn = -195.9 kJ·mol⁻¹

Explanation:

4NH₃(g) + 3O₂(g) ⟶ 2N₂(g) +6H₂O(g)

ΔH°_f/(kJ·mol⁻¹): -45.9 0 0 -241.8

The formula relating ΔH°_rxn and enthalpies of formation (ΔH°_f) is

ΔH°_rxn = ΣΔH°_f(products) – ΣΔH°_f(reactants)

ΣΔH°_f(products) = -6(241.8) = -1450.8 kJ

ΣΔH°_f(reactants) = -4(45.9) = -183.6 kJ

ΔH°_rxn = (-1450.8 + 183.6) kJ = -1267.2 kJ

6 0

2 years ago

Read 2 more answers

A chemist must prepare of sodium hydroxide solution with a pH of at . He will do this in three steps: Fill a volumetric flask ab

77julia77 [94]

Answer:

0.0400 g for the example given below.

Explanation:

pH value is not provided, so we'll solve this problem in a general case and then we will use an example to justify it.

By definition, $pH = -log[H_3O^+]$ .
NaOH is a strong base, as it's a hydroxide formed with a group 1A metal, so it dissociates fully in water by the equation: $NaOH (aq)\rightarrow Na^+ (aq) + OH^- (aq)$ .
From the equation above, using stoichiometry we can tell that the molarity of hydroxide is equal to the molarity of NaOH: $[NaOH] = [OH^-]$ .
Concentration of hydroxide is then equal to the ratio of moles of NaOH and the volume of the given solution. Moles themselves are equal to mass over molar mass, so we obtain: $[OH^-] = [NaOH] = \frac{n_{NaOH}}{V} = \frac{m_{NaOH}}{M_{NaOH}V}$ .
We also know that $pOH = 14.00 - pH = -log[NaOH]$ . Take the antilog of both sides: $10^{-pOH} = 10^{pH - 14.00} = [NaOH] = \frac{m_{NaOH}}{M_{NaOH}V}$ .
Solve for the mass of NaOH: $m_{NaOH} = 10^{pH - 14.00}\cdot M_{NaOH}\cdot V$ .

Now, let's say that pH is given as 12.00 and we use a 100-ml volumetric flask. Then we would obtain:

$m_{NaOH} = 10^{12.00 - 14.00}\cdot 39.997 g/mol\cdot 0.100 L = 0.0400 g$

7 0

2 years ago

based on the positions in the periodic table, which two elements would mostly readily combine to make a stable compound

Advocard [28]

Elements that there Electrons equal a multiple of 8 because then they become a noble gas.

4 0

2 years ago

Explain a natural process, while<br> describe a natural process.

blagie [28]

Answer:

a natural process is water cycle.

Explanation:

during this process,water evaporates from different water bodies ,when the warm water rises,the cold and heavier water comes down to take its place.On the other hand,the warm water on rising,changes to water vapour.

This water vapour helps in the formation of clouds .

When the cloud becomes heavy and is not able to hold the water vapour, it falls down as rain or snow depending upon the climate and atmospheric temperature.

This process continues over and over again

4 0

2 years ago