How can scientists know the concentration of carbon dioxide back to several hundred thousand years ago?

here are the answers to your questions:

• 6. How can scientists know the concentration of carbon dioxide back to several hundred thousand years ago? Scientists analyze air bubbles trapped in ancient ice cores. These bubbles preserve samples of the atmosphere from the time the ice formed, allowing direct measurement of past carbon dioxide concentrations.

  • By measuring the level of carbon dioxide in air bubbles contained within ice core.

• 7. Which of the following chemical reactions describes how carbon dioxide is produced from the combustion of methane. The complete combustion of methane ($\text{CH}_4$) reacts with oxygen ($\text{O}_2$) to produce carbon dioxide ($\text{CO}_2$) and water ($\text{H}_2\text{O}$). The balanced chemical equation is:

  $$\text{CH}_4 + 2\text{O}_2 = \text{CO}_2 + 2\text{H}_2\text{O}$$
  • $\text{CH}_4 + 2\text{O}_2 = \text{CO}_2 + 2\text{H}_2\text{O}$